The wrinkle I see in this plan is the general lack of love for WoW that has been peppered throughout this forum. Also, the greatest strength that I saw for the broader appeal of CoH was that it had the most playable F2P side. You could not access certain content, but, aside from Incarnates, there was nothing to stop you reaching the highest levels without spending a dime.
In WoW, you can't access above level 20 without paying. You can't access above level 55, I believe, without the first expansion, 70 or 80 without the second, and so on. Teaming is virtually pointless, though far less so that in Champions. The mission mechanics are completely tedious, all the more so when you factor in the complete lack of travel powers available to free players.
Has anyone here played to level 20 for free to see what happens? I reactivated my account when Cataclysm dropped and had a fresh character almost to level thirty in a weekend. It would have been faster, but at LEAST half of that time was spent "running" around from mission to contact and back. They don't have cell phones in Azeroth? Yeesh! Anyway, at level 20, can you still play, but gain no experience? Does it boot you and make you start over?
All that said, would we really want Blizzard to overhaul the F2P aspect of CoH to fit their model? I'm not trashing WoW or Blizzard. I've enjoyed every game of theirs that I've played, including the Warcraft series. But, if they were to acquire our game, would we recognize it when it came out the other side?