Disagree with all that:
Ice-T was more socially conscious than NWA and he wouldn't have been a good fit. Maybe he and Cube could have been in a group though.
Redman's comedy/stoner character wouldn't have fit in with Wu Tang's martial arts vibe. Redman would have to make more serious music.
The D12 members came up together so it's best just to let them do their thing. Obie's flow is just too different; could you imagine him on "Purple Pills?"
Mobb Deep's music is just too dark for Nas to blend into and they don't do too many concept tracks
State Property was more into coke rap while Jay-Z is more of a hustler; not necessarily the same thing
Young Jeezy is probably more charismatic than D-Block but not nearly as gully or lyrical. He'd slow down the pace of any D-Block record he was on.