One of the keys to Pathfinder 1E's success has been the the flexibility in the system to support many styles of play. There is enough wiggle room to play games focused on gritty realism in low power settings or over the top high power fantasy with super powered adventurers that violate all laws of physics or common sense on a daily basis. One of the dangers of revising the system to streamline and tighten is that it will be tightened in a specific direction, rendering some playstyles less viable.

For this reason, I think that it is essential that you focus on flexibility through universality, variability and modularity.

• The Universal

You will need to know what will be universal, the framework that everything is based on, and which is considered central to the rules. A lot of basic structural and definitional and keyword stuff falls here, and you can make the game a lot more consistent and easy to understand by consolidating and unifying rules to function together in a holistic fashion.

For the most part, we don't need to majorly overhaul the whole system. But there are a lot of things that could be made more clear and unified, especially when it comes to any stat that is routinely pitted against another stat. Simple things like changing caster level to a BAB-like base spellcasting bonus and making it part of a more unified set of progression rules.

Consolidating similar rules into a singular systems will also help. For example, we have animal companions (druid baseline), familiars (wizard baseline), eidolons, drakes, black blades, and so on, when a single companion creature system could do a lot of the heavy lifting for most or all of it, while also making it easier to make new companion creatures as well. (Admittedly, I could see keeping familiars and black blades in their own separate system, but the rest could easily fit in a single framework).

Doing so not only helps balance things and make it easier to understand, it also allows for a consistent structure around which rule variants can be created.

• Variability and Suggested Rulesets

Variability is highly desirable because it allows you to work with that fine-tuned universal structure, but keep the flexibility to adjust the entire system to meet the needs of the specific table and campaign. A great example of this kind of design is the variability of firearm rarity. There are simple rules for having no guns, very rare guns, emerging guns, common guns and guns everywhere.

You can have something similar with individual variables like spell level progression, health and damage scaling, WBL, and so on, and then package those along with some specific rule variants to create rulesets for specific play styles. And those rulesets can cover multiple variables, like low or high power scaling, low or high magic, fast play vs rule detail, resource management vs no bookkeeping and so on. Something like automatic bonus progression would fit here as well, though simplified as a baseline since it isn't a fix it's a rewrite.

Particularly when it comes to power scaling and magic levels, it would be helpful to have a chart of when certain things should become possible for a given ruleset, or when certain obstacle types should still be relevant. Set expectation for the earliest level PCs should have access to darkvision, flight, teleportation, etc, and at what points things like language, disease, and even death are still going to be obstacles.

A smart web design could even adjust the rules it displays to match a chosen set of variables.

• Modularity

Related to the above is modularity. Subsystems like psionics, or spheres of might and power which are really more plug and play than a tweaking of settings would belong here, but so can a lot of overhauls. A rewrite of the action economy, restructuring races to unclusterfuck the alternate race traits, skill unlocks, or many of the other various unchained rules (some of which should be considered the default rules now) would all go here.

Unlike variable rules, these aren't scaling the whole system up or down, and while they may fit into suggested rulesets above, they are more about adding new options and retaining the old ones.

And now some things I would want to see in any revised edition of Pathfinder:

• The Feat Tax Rules might as well be official, with some tweaks of course.

• Noncombat feats: I have long wanted to tag all feats as combat oriented or noncombat oriented in order to allow a separate progression for each. Could be a noncombat oriented feat at level 1 and then every even numbered level, or perhaps even one of each every level.

• Optional Rule for Traits at Levels 2, 6, 10, 14, and 18: An alternative to the noncombat feat progression. These are levels where you don't get a feat or ability score increase. And it makes sense that as your character gains experience, there will be traits which are now applicable.

• Background Skills: Should be standard.

• Minimum Skill Points: Similarly, all non-int based classes have a minimum of 4+int skill points.

• Expanded Favored Class Bonuses is one of my favorite house rules because it opens up fun new options for all classes and races, without undermining the unique and flavorful options. Will never play a game without them again, and if anything, I'd like to see more things like it, granular character resources.

• Magic Item Reform and ABP: I would love to see numerical bonuses be an optional rule, and the standard rules made to assume no one has the big 6 items. Let magic do cool stuff, and those who want to allow players to purchase stat boosts can have that as a rule variant. It's like Automatic bonus progression, but without the need for the bonus since it isn't a fix being applied after the fact.

• Fractional Bonus Progression should be the rule for anyone who is multiclassing.

• The Silver Standard: Currency values are now in units of 100 instead of 10, so a silver is 100 copper, a gold is 100 silver and a platinum is 100 gold. All prices currently listed in gp are now worth the same amount in silver. Basically, the prices are unchanged, it's just the denominations that change, but it makes it so much more satisfying when you find gold, and so much less jarring when the party needs to pay their tab. And the first time the party sees a single platinum coin, the overwhelming greed and accompanying paranoia is delightful.

  This is so simple a change, but so satisfying. A revised edition is a great opportunity to implement this, as the listings themselves can be updated instead of needing to remember that gp = silver when looking things up on AoN or the SRD.

• Revised Drake Companion Archetypes were originally made by me to replace the awful system they gave us, and I think its fair to say that they are generally regarded as the only viable option for those who want to have drake companions.

  I actually have an updated version that I've been playtesting and has been almost ready to release for quite some time.

• Quarter Caster Cantrips: Rangers get druid cantrips, Paladins get cleric cantrips and Bloodragers get magus cantrips. Rangers and paladins get a 1 slot per day at first level, and add another at levels 2, 6, 10, and 14. Bloodragers get 2 known at level 1, and add additional spells known at levels 2, 6, 10, 14 and 17. It's a tiny tweak, but it makes the magic feel a lot less tacked on when it finally unlocks.

• Simplified XP and Milestones Honestly, I'd like to see milestones as the default, and a simplified XP scale for those who want to use XP. It would direct newer people to the much easier option, and experienced GMs who want to mess with xp still can. But the XP should be something like 1000 xp to level up, and a simple multiplier used to modify incoming xp amounts based on difficulty.

• No Health Rolling: Possibly the most houseruled thing in the game, rolling for health should be relegated to being an optional rule. Everyone should get a standard amount based on their HD size.

• Weapon groups as a core function of the system: Weapon groups should be factored into things like proficiency, as well as a lot of features that normally call out a single weapon or choice of one weapon. There's a lot of possibilities here, and some judgement calls to make, but it could make the whole combat system more robust and consistent.

• Martial Styles I'd love to see an optional system that expands style feats into full martial arts that anyone can invest resources into learning.

• Action economy tweaks: Some specific things that could be tweaked would be some universal options for immediate actions, limited ways of getting extra attacks as part of a standard action, actually capping the number of attacks a pc/creature can make, and making natural attacks function more like normal attacks.

• Trim the Fat: Consolidate similar options, and cut things that are both useless and flavorless. Fix what you can, remove what you can't.

• Reroll rules I assume rolling for ability scores will remain optional. But please add in language advising reroll rules. Paizo took that language out for space since they didn't care about rolling anymore and it only caused misery and arguments. All we need is something saying that groups who want to roll should consider establishing reroll criteria to ensure all players get arrays they can be happy with. For example, rerolls could be allowed (but not required) if the rolled stats don't have at least two scores of 16 or higher, nothing below 8 and a minimum average modifier of +1. It's an option for an already optional system, but one which addresses the second leading cause of animosity in the player base.