ECW fans, while still whores, aren't at the level of TNA or ROH fans in their need to put themselves over the product.
Cena will get massacred at the PPV if he's in the main event. A build to Cena/RVD would be easy, in fact a lot simpler to pull off then HHH/RVD. Have RVD tell Cena he's cashing in his title shot for ONS II and have Cena laugh it off, talking about how he's homegrown WWE talent, their golden boy and that somebody who started out in a bingo hall will never take his title. It would come across better to casual fans rather then the "OMG SUBTLE REFERENCES TO HHH HOLDING RVD DOWN" booking that would take place with the other suggested feud.