I say "slots" out of lack of a better term (that said there ARE limited slots for DLC so your point is moot.) I hate Minecraft with a burning passion. To keep he'd be nothing but a waste, and nothing he can do is unique to him.
I can't believe I'm actually gonna defend Steve in this scenario...
Look, Steve is my least wanted character for Smash period. However, I actually enjoy Minecraft quite a bit and wouldn't mind it getting representation.
As long as said representation is not Steve being playable.
However, to say that he wouldn't be unique is... kinda wrong. This is Sakurai we're talking about, he'll find a way to make each and every character unique, including a blocky boi like Steve. Plus there's a decent number of ways you can build his moveset.
So while I would prefer another FE rep (if my sig didn't make that obvious enough), I wouldn't agree that the slot would be wasted on Steve, despite how much I don't want him in.