traitor gaurd could easily be a suppliment for astra militarum. really, youd need rules for marking units, the addition of some if not all the chaos vehicle armory, some unique characters and perhaps a different list of orders, maybe not completely different but with some newer flavors.
csm itself shold be broken into 2 dexes, methinks, one for renegades, one for legions. bring the named characters in line with their heresy counterparts, in terms of power and wargear. and definately do away with the compulsary challenges.
and for certain, the named characters should not even have access to the boons and mutations table. its silly to think that kharn might end up a spawn, and none of them need the bonusses.