DMX has made his dislike for Drake pretty clear. Though he and Weezy seem to be cool, it would probably be a bad idea to sign to a label whose star artist upsets him. Not to mention, X doesn't need to add his controversial behavior to the mix.
There are multiple reasons why J.Cole shouldn't ever sign to YMCMB, but two stick out the most. For one, there would be a never ending battle fo the spotlight between him and Drizzy who have already been heavily compared. But currently being Roc Nation's shining star would be the biggest reason that a deal with YMCMB would be a no no. Cole would be adding to whatever beef or competition lies between Hov and Weezy and things could get pretty sticky. We know it's a Cole world but that would really be COLD.
With Nicki Minaj reigning as YMCMB's first lady, Trina shouldn't ever head in their direction if she wants her music to ever see the light of day. Between Nicki Minaj, Shanell and now Christina Milian, YMCMB's space for female artists seems to be becoming more limited. With her new transition to pop and her hip hop past Trina is sure to be battling for a spot against Nicki that she's more than likely to lose.
Tyler, The Creator
Tyler, The Creator seems to thrive being on his own. Between his erratic behavior and spotaneity and his diverse range in musical production, he may be better left doing his own thing. Though he makes beats that he wants Weezy and his gang to rhyme over, signing to Young Money might stunt the Odd Future member's growth.
If Wale signed to YMCMB, he might lose some of his characteristic artistry. While YMCMB is taking over commercially, fans might be upset to see Wale completely making that transformation.