That sounds good but I'd be worried that MS would not allow Volition to make Saints Row as crazy as it is now and will not want to upset studios like Rockstar (so they keep timed exclusive DLC). I think if Volition are allowed to do what they want and MS back them with cash and promotion then it will be great.
If I were MS I would swoop in for Saints Row.
I would also like Microsoft to buy the other studios Relic Entertainment, Vigil Games and THQ Studio Montreal (if THQ has to be split up).
Microsoft could give the Age of Empires franchise (and any RTS games) to Relic Entertainment and have them really push PC game development and develop console games of any genre (although I'd play a Relic developed Halo Wars 2).
They could then get Vigil Games to make some more Darksider games or some games to compete with either God of War and/or Zelda.
As for THQ Studio Montreal it's a little too early to find out what they are doing but Microsoft does have the money to build out the studio and support whatever game they are making.