It completely depends on how we're going to set the team up.
If we're going to play with an attacking midfielder, then he'd be a good option. Still a bit inconsistent, but frankly if he wasn't then he wouldn't be playing in the Championship. I don't think it particularly matters if he's "lightweight" in that position.
I don't rate him as a winger or central midfielder though, so if we're going to play 4-4-2 or 4-3-3 then I wouldn't sign him.
If I were the manager then I'd probably be going with 4-3-3, but that's not the only set-up that could work with the right players. No objection to signing Piazon as long as Brian's planning on using him correctly.
However, if we were going to splash out on one of our marquee loanees, I'd rather have Vydra. Piazon would be ahead of John, who in turn would be ahead of Fernandez.