Kevin Levin (Ben 10) / Absorbing Man (Marvel) type character, how would you do it?

Hi, first post, been lurking around this community for over a year and a half now!

So, I've seen the character sheet from the Jab's build dump on the Echoes of Multiverse forum, but still I'm not so sure with that is the right direction that character would go, so I am posting here to hear what y'all have to say.

The character would be basically a matter and energy sponge, if he touches rock he becomes rock, and could shapeshift its limbs into a variety of weapons because of it. In case you know the character is basically Kevin 11 from the Ben 10 series.

So, how would you do that character?