One thing that frustrates me in the world of games is the cursed insistence of game companies on changing the control system from one game to the next.
Particularly if the game is a good one and you invest many hours submerged in its world, learning its mechanics, you get very accustomed to its interface, and your brain and muscles learn the pathways you follow for perhaps hours every day.
Two examples spring to mind, one on each side of the coin.
The Witcher was much criticised for its control system when it came out, but if you liked the game and played it more than once, you learned how to use it, and you had a great time. That time revealed itself to be completely wasted when the Witcher 2 came out, as the company threw out the old system and you were forced to learn a new one to play the new game. It put me right off.
Having played Greedfall more than once, I became very used to using the right mouse button as the "Back" button. Playing M:WL, and older game, I was constantly getting tripped up by the fact that the RMB worked as the "Back" button to close every pop-up screen EXCEPT THE FRELLING MAP, for which you had to hit "M" or "ESC". Lo, when I played The Technomancer, the RMB worked as I felt it was supposed to. Hooray for Spiders!
Which brings me to the point, the question. When mashing the three Mass Effect games together, are they going to use the ME1 control set (which I liked) or the ME2/3 set which was all different for no good reason I could fathom, and required learning anew after getting used to the ME1 set. Perhaps you'll have to use a different control set for different chapters in the game? (No, no, nobody woud do that, would they?), or perhaps they'll rework the interface of ME1 to use the same control set as ME2/3 (which I will find annoying as I'll have to unlearn what I've long known). OR, perhaps some genius will have decided that the previous systems were all flawed, and there'll be a brand new system we'll have to learn.