This seems counterintuitive? he wants to eliminate the saiyans, so he breeds a saiyan with a half-saiyan, to maximize the saiyan DNA (since in GT, there are no living female saiyans)
@memyselfandl I'm pretty sure they said in GT that once Baby infects someone it rewrites their DNA in some way, hence Vegeta's change in appearance. So if that is true then Bra would have one of Baby's kind instead of a Saiyan.