It would be a little risky, having a company create supplements they regulate could
A) Open the door for them to create banned items but make them "Allowable"
B) Use their power to essentially destroy other companies either by falsely marking them as unsafe/risky/tainted or pretty much forcing all athletes to take their supplement.
USADA should stay in the regulation game and UFC in the promotion one. Let other companies create the supplements and allow USADA to be independent when testing. Then perhaps, like Mongoose above mentioned, they can create products that can withstand scrutiny, to which they can then promote as "Safe for competition"