Overall less cartoony visuals, more dark, scary, and realistic
More fidelity to the original: Shrykull's blue ripples and blue curved lightning instead of yellow jagged lightning, removal of the new 'chant chakra' thing - or at least dial it back so it's not just a bright blur of light, less goofy shock-gate death animation, if it's absolutely necessary to show the bird halo when chanting - only show it when you've taken damage - and don't show it at all on hard mode, don't include warning signs over every possible pit you can fall into - or at least don't include them in hard mode.
Shadows instead of steam vents!!!
Controls that move more realistically and feel more responsive - less beta-ish
Scrolling text signs that are black with color text like they were in the original, not orange with black text
Way more variety of idle dialog for NPCs, don't rely quite as much on jokes and try to get at least some serious dialog in there, and use it all less frequently so it doesn't get annoying or repetitive
Cutscenes that look and animate much more like the original, more realistic and immersive than NnT's were:
https://encrypted-tbn3.gstatic.com/i...1nn1CdiJRsjRaM
I know Abe's Exoddus had some silly jokes in its cutscenes like Abe painfully landing on his crotch in Necrum (even though slaves don't have any genitalia?), but they should probably cut back on some of that in my opinion.
I'm probably forgetting something but there's a couple of things that weren't in the original that would be cool to see in the remake:
Actual co-op with two players collaborating on the same screen - and put this in NnT as well. It would attract so many more people to the games.
Variety in the scrabs and paramites, maybe slight variances in size, or slightly different breeds native to the vaults of Necrum
Maybe an added Elum sequence in Necrum?
An easter egg - blowing up the sealed-off door in FeeCo depot to RuptureFarms lets you go inside and see a rusty dilapidated version of what used to be there ... maybe something similar for the door to Vykker's labs, like a glimpse at some Vykkers