They're both also legacy acts who could perhaps have one more good-to-great project in them. It's surprising they haven't collaborated before. Might have been a killer combo in the late-90's. Both somewhat straddle a line between genres (Lenny - Rock and Soul, Janet - R&B and Pop and Rock).

Out of the other names listed above, Saddiq would be interesting as would No ID. No ID seems to bring heat no matter the project. Raphael's legacy is unquestioned and he's also another artist who maybe has one more remarkable project in them.

Salaam would make for an intriguing combo as well.