Displaying engine damage by reading memory was in my opinion a cheat and I did not like it. Not a big deal but it was one reason why I never used that program. (Yes, I know that newest LFS version has engine damage display for everyone, so it is fair now)
Another function I do not like is "Radar", no matter if it is done by normal Insim or by hooking into LFS.exe
I am simply not a fan of too much on-screen GUI in sims. For many car classes it feels out of place, too high-tech. I feel that being aware what happens around your car (mirrors, sound, looking around) is an important skill. Radar goes against that. However, on some setups with small screens can be hard to do that so I do not mind if people use it.
I am not aware of anything else.
Sometimes broadcasts use overlays for position lists etc, I do not know how they do that. I am okay with whatever way they do it because it is only used for videos, not for racing.
If LFS get modified too much there might be a risk of breaking multiplayer?
I would not like if some races required manually downloading modified files because that is always a mess in other games. (I think in LFS that was only done once for a NASCAR experiment, before mods system)