Free to play Halo ? Am sure you have added it in the list to cause a stir CVG...naughty.
The only way to maintain the balance in Halo is not to introduce "pay to win" into its structure. You mention monetising things like top hats etc...no need - the Spartan Ops missions in Halo 4 will be subscription based, only season 1 is free.
My list of console games that should be "pay to win"
Twitter - @richomack360, XBL: richomack360
R.I.P. Rik Mayall - British comedy has lost an icon and a jolly nice b'stard.