I guess the real question I have is do the rappers need to solely manage the labels and does signing a JV deal with a label subsequent to forming a label disqualifying?
When Roc-A-Fella formed, it didn't form as an imprint under a major record label. It was its own label that went for a distribution deal (same way you'd see indie labels sign deals with Caroline, Fontana or Koch, E1, etc.). But it was a true indie label for a good hot second.
Obviously, E-40's Sick Wit It & No Limit were founded by rappers. Sure, Birdman may not have started as a rapper, but Cash Money counts too. Ruthless Records was founded by Eazy-E to spearhead NWA releases... Eazy didn't want to rap at first, but he did. Tech N9Ne has his own label too.
DTP, Jeezy's CTE, & T.I.'s Grand Hustle started as indie labels before signing distribution deals.
These are some examples.