Not much you can really add too it without making something already in place with a purpose lose its purpose.
Make it drop lv 60 Earrings ? idk still got a fair influx of those floating in the game from the last even that poured out earrings.
lv 50 Necklaces? Takes half the purpose of DMHM away
Amara bosses already shooting out the Same stuff as TTC but only in a fraction of the Amount.
Boss cubes makes it pretty easy to have naraks and kilos.
Medals aren't too hard to acquire.
Epoxy and Metal scrap drops from like everything as it is.
Skill resets drop from bosses
Spanners and Ancient spanners drop.
Pretty much everything is already acquire-able either from bosses or TTC, other than maybe 2 things, Beta Hexes ( I know they drop in DMHM but not very frequent) and Safeguards.
And again not to leave out what I already said about TTC pretty much already outshining bosses in the current state of things. Evening doing the Amara bosses aren't even that enjoyable, and much incentive to fight over anymore because of TTC, Smog can easily be forgotten about and even cut out when there's 5 other bosses in Amara that can use adjustments first.
Before TTC, Boss loot was a main source for things, other than uni weapon skins and costumes. Now it's like why should I do a boss and maybe get 1 boss Treasure replicube and maybe a metal scrap when I can do a TT or TTC run and get like 10 jewel replicubes, 10 ancient jewels, 4 spanners, 2 ancient spanners, 6 Boss treasure cubes, 2 metals scraps and 4 mech shards and if not even more.
Unless you're ready to just make every boss in the game Loot-splosion with nothing but uni gear, accessories and misc that fit the 65 cap area and make everything else in the game added prior up to this point just pointless. Cutting out 1 boss wouldn't hurt at all. ( And I know there's other items that could be tossed in that wouldn't due to it's a way that helps keep the game funded by having certain items exclusively to AP Purchase)