While I don’t envision a “re-mastered” edition of Mass Effect to realistically go too much beyond the cosmetic side & maybe a couple of major bug fixes, but since this is a wishlist here is my 2p on it.
Unified graphics engine, with as many FMV sequences scrapped and done via the game engine wherever possible, FMVs in general just haven’t looked the part anymore. Ideally as well there would be a unified combat system, or at the very least a fixed system for ME1. Get those bugs fixed that can cause havoc & sometimes even forcing game reloads, particularly when using biotics.
For the love of god please fix the cutscenes for all 3 games to show Shep & his squad the weapons they actually have equipped and not the generic Avenger rifle, that’s bad coding man!
Sort out as many save import bugs as possible, particularly the ones between ME1 & 2.
Assuming same combat system gets put in place for all 3 games, have a seamless character levelling process put into play that can’t be completed until ME3. You can cap at level 20 in ME1, 40 in ME2 and finish at the 60 by ME3.
Get rid of the thermal clips, there was no need to retcon these in for ME2 & 3, the fact there are places that continue to spawn ammo after you’ve picked up means the devs know themselves that system doesn’t work. Just get rid of them, and go back to the heat system with some weapon mods that affect cooling etc in the same sort of spirit some ME1 weapon mods did.
As much cut/incomplete content finished and put into the story possible, and access to completed content that was blocked, e.g. it’s possible with a mod on PC to have Legion, Tali etc for Horizon mission in ME2, but to prevent constant disc swapping on consoles this got blocked off to all players.
If any story/script elements could be fixed or improved I’d be in favour of that too, little things like Shep knowing about thermal clips at the start of ME2 when s/he shouldn’t, and squad members not wearing sealed suits in toxic environments/vacuum.
Agree with the comments made to streamline/get rid of decryption & scanning mini games from ME1 & 2, but assuming there would be a unified combat system this would remove most of the item pickups in ME1 anyway so there wouldn’t be much mini games needing doing.
That’s about it from off the top my head, the chances of getting anything new is slim of course, so if they could at least make the engine more accessible & easier for modders to do work. That would be a good compromise under the circumstances.