I've been keeping an eye on this for awhile now since the rumours started. I'm really looking forward to it and hope they actually put effort into it. The biggest problem with remastering the trilogy is the first game. The second and third games play fantastically well but could benefit from the expected updates, i.e. hi-res textures, updated lighting, 60fps (at least), better controller support, and faster loading.
As for the first game, it needs way more attention. The biggest problems are the UI/inventory system and the combat. They basically need completely overhauling which I imagine would need the environments to be altered to work with a proper cover system, and character movement would need to be sharpened up because it's way too slow and clumsy. The game had a big issue with texture streaming and pop-in (even on modern PCs) that needs to be fixed, and also tweaks to the Mako. Oh and the loading times...
Also while I don't like the ending of the trilogy (to put it nicely), I personally think it's best if they just leave it at this point... unless they hire Drew Karpyshyn to come in and write a proper ending, one that the series deserves. That would blow my mind
