Ya, I feel what you're sayin. I've seen a lot of mix tapes with featuring Lil Jon, 50 cent, but it's just the original song with a new verse laid on it. Not really featuring.... That's why if you are going to do something like that, you want to kind of remix it. Remember to say it's a "Mix Tape Remix" and not a song featuring the artists. It's featuring you as a remix...
So ya, be careful how you promote those songs. It can get you into problems...
Also, remember you can always get San Quinn, E-40, and others from the Bay on an original song. Yes, you will have to pay them, but it's worth it.