Personally I would be more for a graphical style like FFXIV or Persona/Catherine (as much as I don’t like Catherine) - something that kind of isn’t old-style sprites yet isn’t FFVIIR or The Last Of Us 2 either. Having played FFXIV I can say doing Gear combat in that visual style would be amazing (can you imagine Weltall-ID in the style of the Primals?)
I would say the platforming could go or stay, although I would like an official save state/skip option in if it stayed, especially if the Babel Tower platforming is changed to be like the Kugane Tower/Leap of Fate from XIV (nooooooooooooo)
TW: mental illness, dissociative identity disorder, spoilers:
Spoiler
DEFINITELY would like to see the entire mess they made of DID fixed. Like seriously, get a system who’s a sensitivity reader capable of handling this shit without being triggered or upset by it and consult with some actual therapists like say Bessel Van der Kolk and rewrite almost everything dealing with the Fei system OR OR OR leave it as is, but put in context that clarifies that everyone is being so awful and ignorant and “treating” Fei system in a way almost guaranteed to make him snap a few years later and make Id kill off all the remaining survivors for hurting them is because their psychological knowledge is limited thanks to the Gazel’s oppression or something.
Would definitely like Disc 2 to be fleshed out a LOT more. Would love the world to totally be built out on the idea that it seems to be in canon - where there’s just so much to explore, neat little details everywhere, the setting of the planet just almost being its own character of the setting. That’s stuff I love about the game and I would love to see more of it, just the setting of the world given more expansion and life.
Sigurd and Ramsus as playable characters at some point or other.
Liquid Sky being a bridge between the ships’ crash and Lahan, and ideally with playable Sigurd from the above, getting to walk around and explore Etrenank/Etamananki from his point of view at the time, and getting to plan and execute his escape from Solaris and Bart’s rescue from the palace… and also would like to do that entire thing where they’re freeing Bledavik as an active time event, where you’re with him and Citan there AND with your party at the crypts going after Andvari…
TW: reference to relationships, proposal of choices there
Spoiler
Also would like to see the entire Bart/Margie thing dropped completely (seriously, incest is not cool and just makes everyone look grosser for it). And for as much as I like Citan/Fei and appreciate that subtext I notice between them, I would say it should probably be dropped/cut because of how it would come off as grooming/horrifically problematic to people who approach the text with a post Voltron anti mindset where any such hint is problematic/upsetting regardless of the characters both being adults, where the modern fiction critical approach is less “is it the safest/best you can get within the setting with the characters and are they both consenting adults within that world they inhabit” and more of “it must conform to 2015+ US IRL standards of what is allowable and moral.”
I would support the idea of giving Fei the choice between Bart and Elly and making that a love point/decision point setup where you can get either path (because there’s nothing truly objectionable on either an ethical or a canonical basis with Bart as an option for Fei - same age, they first meet when Fei is 18 so there’s not even a place to assume things could have been grooming, same effective race within setting and same knowledge/intelligence level as both Lambs, he’s as much of a reincarnation as Elly is, etc) because I think that would be cool, but then that is just me.
Would also like to see an alternate ending mechanic inspired by the Zohar Probability Modifier + the game’s originally going to be a Chrono game that includes that above thing but also more: What if you somehow disabled the Gaetia Key? What if you have the option to actually make peace with Id and treat him with respect rather than just erase him? What if other junctures in the setting went different ways?