I feel like maybe your problem is more with the instrumentation itself rather than the composition Brandon? Because ReMixing IS sampling a section of a game tune to your own piece of music (composition). And in the case of samples that people buy and have consumer rights to use then those aren't even part of a published or completed work, just an idea that's been put into a small WAV file. Very similar to something like a snare sample, or cymbal sample, or a flute sample, guitar sample, synth preset, etc. I don't see any major problem using those either since most samples those now a days.
Really it just seems like you're making a big deal out of something that isn't. :/