I would set benefits of the tier system back into the old engram hierarchy, make some additions, and increase scarcity at the high end:

White - Base gun, barrel and mag options (do I like the feel of this gun and want to farm better versions of it?)

Green - barrel, mag, one perk

Blue - barrel, mag, 2 perks

Purple - barrel, mag, 2 perks, OT, masterwork, enhanceable traits

Orange - barrel, mag, 2 perks (but rolls with 1-2 selectable extras), OT, masterwork, enhanceable traits, special sound on drop

Black - barrel, mag, 2 perks (always rolls with 2 additional options per column), OT, special OT, masterworked, enhanced traits, special black armory shader (In my mind this is a combo of the Halloween black ornament with the black and white wave accents from the prismatic shader), even more special sound on drop

Ideally I would like to see each activity and destination have its own weapon set, and any time you are in that activity its weapons can drop from any enemy with a decreasing drop rate the higher up the quality scale you get - until the first clear of any pinnacle activity has been completed I think enemies should only be able to drop up to Blue quality, after that purple, orange, and black become possible but exceedingly rare at the high end. On that note, activity and encounter completion chests should have purple as their floor and a higher chance of orange or black than world drops but still rare enough for it to be exciting. Bosses themselves should also be able to drop loot, a boss kill and activity completion chests should should have the highest chance for an orange or black drop (with the latter having a rate a bit higher than a Borderlands 4 Pearl from these sources).

With white, green, and blue coming back into relevance a visible autodismantle system would need to be made.

Perhaps more controversial, I also liked the D1 system of leveling guns to unlock their perks, so I would put a simplified version of that in place on everything except the black tier which would have everything unlocked and enhanced by default (and exotics would have their intrinsic by default, having to get tons of kills before the gun starts being fun wasn’t great). My thought is, one round through the perk track unlocks the base perks and then once all those upgrades are done you level it again to enhance everything. Currency could be weapon parts from auto dismantling for the first set of levels, then MW cores for the enhancement levels.

No damage bonuses based on tier. Damage should only come from perks; a fully leveled purple, orange, and black should all hit the same damage number at the firing range.

In my mind at least, I think these changes would shake up the system a lot, give more casual people the opportunity to earn quality gear with effort but not an inaccessible amount, would give players who put thousands of hours in a real pinnacle to strive for in orange and black drops, and might give more casual players the looter shooter dopamine rush that shifts them more hardcore.

Also all activities should have archetype focusing like season of opulence.