The limiting point is an interesting one, I had a chat about this with Mod Rice a little while ago who brought up an interesting point around how reward space can kind of 'expand' and 'contract'. You absolutely can argue that it limits future upgrades, but having a 'tier' of reward that ultimately introduces new BiS by eliminating switches doesn't creep power too much, and then you can follow up by expanding outwards and getting style-specific upgrades again rather than just flat-upgrading a tribrid boot, which brings back another decision for people to make.
Totally appreciate this reaction because my initial one was similar, but I think my thoughts have changed with it being framed that way, I don't think it's a limiter at least!
Note that this isn't a project I'm specifically attached to, but thought that might have been an interesting point to share on this specifically!
EDIT: I remembered Rice's example! Amulets! Start out with basic 'style-specific' amulets (Accuracy, Magic, Strength, and we'll ignore that Strength is actually really good), combine them all into a Power, move to a more offensive option with fewer defences in the Glory, Fury brings them back together again, then Zenyte Jewellery splits them out again. All that to say, don't think the approach has to be 'we have a tribrid boot so can only make better tribrid boots', if anything I think being in this position might give the team more room to spread their creative wings!