What is the feasibility of an independent music label releasing an
album featuring 3 major label artists?  The label has its own
distribution.

The 3 artists must have each released a platinum selling album.

Genre does not matter.

The album has been written and all the artists have to do is perform
the songs.  Each artist performs 4 songs.

What might the labels request in return for allowing their artists to do this?

What might the artists ask for as compensation (up front fee + album points etc)?

I understand that there are a million variables that go into something
like this, so i know that the answer will be greatly based on opinion.
 But opinion must be that of someone with a good understanding of
music labels.

The only example that comes to mind as an example is R-Kelly Jay-Z albums.

$10 tip Bonus: Approximately how much did artists recieve to appear on
Santana's Supernatural?

thank you.