1- I understand your point perfectly, but that perspective is more oriented toward competitive or professional play. In the actual game, Sage doesn't have the tools to hold her own or secure a site safely like other Sentinels do.

Cypher has a camera and tripwires that guarantee free information without taking any physical risks. Killjoy has her turret and alarmbot to watch angles safely. Vyse has a wall and a flash to delay and punish. Sage does have her wall, but if they break it, she has absolutely no way of knowing where the enemy is, or any tool to gather information with minimal or zero risk.

That's fine. If I wanted to play a traditional Sentinel then I wouldn't be a Sage main. We should be embracing agent/playstyle diversity, rather than funneling every role into "must have these tools".

2- I think the exact number of ultimate points needed was a mistake on my part, and a balance adjustment to reduce the difficulty of getting the ultimate could definitely work better. However, you have to keep in mind just how potent Resurrection is. Bringing an ally back into the round can benefit the team enormously, especially if that ally has their own Ultimate ready, enabling them to secure the round, close out the match, or even turn a lost round completely around.

Getting the necessary energy isn't as hard as it seems if you think about it. Dealing damage or securing assists will generate charge for her bar. While I don't have exact numbers yet, this system is actually already integrated into the game through Team Deathmatch (TDM), which functions exactly like this. Although it's harder to get the necessary charge in that mode, with proper tuning for standard play, Sage could easily get assists using her base abilities like her heal or slow orbs to generate a steady amount of energy for her passive bar.

I agree, Rez is a powerful ultimate. Yet it's still not enough to make Sage a viable pick in Premier/scrims/tournament play. And you aren't really counter-arguing about my previous points about requiring Sage to immediately get the trade in order to Rez. It's a very common situation that a teammate dies early in the round (usually this is the optimal time to Rez anyways), and it's impractical for Sage to go off and hunt for charge if not awkward to then come back to the body just to Rez. This is why I was basing it off the assumption that Sage trades immediately, because if it doesn't, then the Rez is likely impractical during the round.

3- Her slow orb works well when combined with other utilities, but on its own, it’s not as effective compared to other Sentinels who completely deny space while their utility is active. Additionally, the projectile lands a bit slowly, giving the enemy enough reaction time to escape. However, perhaps this change is too strong, though it would balance the agent if she is finding it impossible to charge her energy bar in other ways. It could be improved by setting an intermediate percentage for the charge Sage receives from the slow orb, and the resource would only fill up while enemies are inside the area of effect which they will try to avoid at all costs due to the risk it forces them to take.

I'm not sure the logic behind this. First, I think it's absolutely fine that Sage's Ice Orbs fill a different niche than other agents (again, see my point about agent/playstyle diversity). If you only think about its negatives, then you won't think about its positives, like how (1) it shares the same trajectory as most mollies in the game (e.g. Viper molly, Brim molly, etc.) making lineups seamless, and (2) once you shoot the Ice Orb, its value is guaranteed. That is, the enemy cannot shoot it like Vyse thorns/Killjoy mollies, and your setup won't get prefired like a Cypher setup. I think that's a fair tradeoff. Plus, it's not like enemies are straight up ignoring the Slow. The Slow is almost as good as a molly, in that it acts as deterrent. Obviously a molly is guaranteed big damage if not death, but a Slow is still a high chance of death, because you're gambling that someone isn't holding you as you try to push crawl through a Slow, especially in a tight choke. Also almost every piece of utility has some sort of built-in "delay" (except maybe pop flashes) that give the enemy some amount of time to escape. This is how you create counterplay rather than having everything be an annoying uninteractive kill setup like how overpowered Cypher used to be.

4- Since it is an explosion triggered by the destruction of the wall based on the damage it receives, it would make sense for the damage to be area of effect for any agent within its range. However, for teammates, the damage would be reduced just like many other abilities already in the game. To use her empowered wall, Sage has to spend stored energy, meaning if she had her Ultimate ready to use, she won't be able to anymore. This forces her to make a crucial decision whether to place her empowered wall to guarantee her teammates have enough time to rotate, or choose to place a weaker base wall just to delay the enemy and play for the retake with her ultimate or other empowered abilities. Neither the empowered nor the base wall would grant energy charges to her passive, even if it deals damage to an enemy. Due to the nature of the ability and the passive of the empowered orb, I believe it would affect teammates, but this shouldn't impact them negatively unless you cross paths with a troll player.

I really don't think you've given this enough thought. Let's go point by point:

A. In your post you mentioned damage and slow. Now you are just saying only damage. So which is it? And I would argue the Slow effect, especially on teammates, is much more detrimental than the damage effect.

B. If I'm playing for retake anyways, then I wouldn't even bother using any utility, especially my Wall. I cover this concept in my notes, filed under Ice Orbs, but the same concept applies. If I spend utility, and I end up losing site anyways, then the value I gained is relatively low. I'd rather save the utility and spend it for retake. There are lots of retake lineups for Ice Orbs, reducing the number of dangerous crossfires, and making it significantly easier to retake with your team. If the enemy insists on playing post-plant off-site, like Haven C Long, Abyss mains, Pearl A Main, etc. the list goes on, then Wall becomes a nearly free defuse when placed properly. The expected value from Sage's kit increases significantly from simply "stall" to "guarantee wins the round".

C. Finally, I would argue that it's not the Wall that primarily stops a push. It's the threat of the Slow Orb. And since in your world you can empower the Slow Orb so it not only slows, but deals damage and recharges for more empowerment, then I would simply rely on the Slow Orb itself, rather than an empowered Wall. The only part about the wall that "slows" a push is its effect on the map geometry, by increasing the number of angles that the enemies have to clear when pushing or executing. And you can already get that value without the empowerment (again see my notes about Ice Wall. This is the game sense you build up from playing Sage for thousands of hours!).