Not a good strategy to keep such a narrow focus. If you take out Saddam but leave the Baathist power structure intact, you'll have a thousand Saddams waiting in the wings. This is little better than the unfinished job of 1991.
It stinks to have to do this, but we need to stick around long enough to eliminate the Baathists from the political equation permanently.
That's too tricky and we're not qualified to do that, and besides, it goes beyond the agenda stated by Bush, which did include "regime change" but not necessarily elimination of all Baathists from the power structure.
In any event, ensuring good behavior by a new regime depends less on whether the leaders were ever affliated with the Baath party and more on whether they respect the US's ability to personally punish them (read blow the out of their bunkers) if they misbehave.
Remember that Reagan effected regime change in Libya without even changing the leader, let alone eliminating all affliated with the leader, by blowing away the tent Quadaffi might have been sleeping in. That shaped him up pretty well for a while. We're dealing with animals here; we have to treat them that way, and not overestimate our ability to control their complicated politics.