The issue with Cena/Wyatts isn't Cena. It's not really the Wyatts either. It's that due to this feud, the Shield now have nothing to do. Had WWE not rushed it and forced the match into the Chamber PPV, Wyatts/Shield would've felt huge at Mania. That's the Wrestlemania match that both the Shield and the Wyatts need. Not Cena and especially not NAO/Kane.
On Cenas end, any match he's involved in would feel big. I'd rather see Cena/Taker, though. Talk about a big match.
Lesnar would need a new feud, and the best I got for him is JTG. (Okay fine... Sheamus)