Mastermind is pretty worthless here, but the main intention is to remove action tokens from sidekicks. I'm not exactly sure if all sidekicks are going to be grouped up to take advantage of this though. However if they are and you are working the Robot Thing engine, he could be quite good.

I don't see why you should play him unless you desperately need a low point leadership or you bring a super sidekick heavy team

Yea, unfortunately this is the only future foundation kid I see absolutely no use for (and he’s one of my favorite kids from the team!)

If you really need leadership on a Fantastic Four themed team he is cheapest option up to the set. Plus he has added bonus of group token removal. Actions are important and I have looked for the cheapest way to get extra leadership. His mastermind will help keeping your action pool too. If you are playing a sidekick based team leadership will be important especially in 300 point games. So at 1st glance he looks useless when building and looking for options to advance action total he shines at 20 points.