I think Memotech MTX is at least one that you can pretty much drop out. I actually ported my AI based MSX game loader for it (I originally made it for SVI-328) and during the process I did learn quite some details... The fact that it runs on 6MHz while MSX runs on 3.5MHz and the sound chip is different is probably not that big issue... but I think that the fact that MSX lacks the CTC chip will be a thing that you can't overcome in any generic way. This chip is used to do things like cassette load, but also all other kind of timing related stuff. If the game it self is not using it for anything very important, then it might be possible to port it, but this means you have to evaluate each program case by case.
