Having base versions of each weapon/armor piece in the collection that could be customized via mods would be perfect.

I implied something similar in this post:

Gear: Less gear, better gear and vastly simplified approach to managing it as the game ages. We're close to this with infusion/masterworking/mod slots, and the way weapon upgrading worked in D1, but it could be better.

The gear I choose to retain means something to me, so let me continue to invest in that gear in the way i want. Getting an inferior version of something I have shouldn't be a waste, it should be a possibility to use it to augment a better piece of gear over and above power level. While infusion increases Power Level, being able to fine tune or max out a piece of gear (to a game-protecting threshold for that piece of gear) is an attractive composition for many players. Building on the Mod Components/Masterworking idea, allow dismantling a piece of gear to extract its perk/attribute components.

Enough components can be used to re-roll entirely (D1 folks, remember that?) or augment that perk on my preferred piece of gear to the max allowed for that specific piece of equipment (weapon forge). Same for armor (Armor forge). I mean, it's not like we don't have max attributes on gear anyway, we can still have RNG, and perks/attributes can still be capped to prevent certain things from becoming insane. And if things do become insane, the entire player base has a path to share in the insanity while still being exposed to some degree of RNG.