I mean they do try to lock down the client, but the thing is the majority of anger comes at cheaters in games that are designed to have players compete against another, like CounterStrike, The Finals, RUST, COD, Battlefield, etc...

Community servers and co-op games that don't have the same structure usually have less problems with that sort of thing. I haven't played Mass Effect 3, but if it's a co-op game I'd imagine players would be more okay with it (especially if you explained what you're doing) compared to something like a CS2 competitive match.

(Also some games like RUST make a clear distinction between official, community, and Modded Servers, and allow the host to pick their own rules. You could find a modded or community server that allows that sort of behavior, for instance.)

Edit: also, there are games with intentional modding implementations for co-op and server multiplayer play, like Project Zomboid.