I like the idea, but its the streak! I dont think the streak should ever be broken. Plus WWE would probably realise how much money in merchandise they would lose then have him cut a cheesy promo the following night on RAW about how he snapped etc and be exactly where he was before mania.
Plus it wont make Cena into anything more than he already is. If you want him to matter outside of the WWE world then he needs to be involved in the celeb thing, like he was with K-Fed, maybe he should have been in trumps corner at Mania 23, saving Cena v Umaga for then. Cena is already a multi-time champ, he is already the biggest star they have.
Takers streak has been made so sacred now that he must face only a select few at Mania because it creates the interest of whether the streak will end or not, like this years mania, but it would be wasted on a guy like HHH or Cena and a younger guy isnt 'worthy' of ending it.
They should do the best thing and keep it intact, Taker probably only has a few manias left in him so he could have HHH, Cena and Sheamus to keep the interest going, then maybe after a couple of years a comeback against a new fully fledged top guy like DiBiase.