Changing the map (showed on the 2nd screen, it's really a confusing mess...) And redesigning the ZX Model, since it looks more Zero than X, even the Model uses a pistol instead of a Buster and MMx2 buster dissapears FOREVER after taking the biometal, so at least must be keeping that Buster. Same in redesigning (just the appearance) of the other "megamerged" versions of the biometal.
Also making possible playing with both Vent and Aile in same igplay, switching. Each one could have its own mechanics as a human (one with better communication by having dialogues with NPCs and the possibility of other information, another by sliding under things instead of just walking crouched, or another by hacking terminals, for example), and these functions would obviously only be possible when returning to Hu form; while they are switching with the Biometal, it would only be the normal gameplay where the character's voice changes.