My short list would be:
Buff Archimonde
Combine lower tier ascension relics to make higher tier ascension relics
No more titan tickets (c'mon with that...)
Upgrade rewards for titan (token counts are low (IMO) and takes too long to accumulate)
Recycle/Trade System
Examples...
Recycle/trade a mythic item for 3 transform relics
Recycle/trade legendary items for tokens
Recycle a divine item to mythic level 50 to regain some or most of the ascension relics that were used to divine it (i.e., in the case of item changes (i.e., monkeys))
Some sort of dupe reduction for premium drops, or special type of box to choose what type of drop (For example: I have no premium swords, and no premium energy shields, but 12 claws and 12 rolling beasts...)
Smarter auto-upgrade system, or just any type of QOL update here...
Currently... it will auto-feed a lvl 20 blue kit to a level 1 white kit...
I try to be efficient, and so will not feed 5 blue items to a grey kit, but 4 blue items and 3 or whatever white items. It's is not difficult for the auto-fill logic to do this for me, instead of making me upgrade items twice.
Inventory space
@see https://community.supermechs.com/topic/767-grind-the-introduction-item-limit/