There's a general agreement that small guys like Frankie Edgar could have done what Royce did. But what about women? Even if she could beat Royce Gracie, I can't imagine even women like Cyborg beating huge guys like the 6'11" Gerard Gordeau.
Seems extremely unlikely. Look at what happens in other sports when women compete against men -- and this includes sports with way more history and depth for women than MMA.
For instance, the Canadian and American women's hockey teams -- the only teams ever to win Olympic or world championship gold in women's hockey, play and regularly lose practice games against 15-16 year old local boys teams. And that's playing without allowing body checks (no body checks in women's hockey).
The Swedish women's soccer team (Olympic medalists) lost badly against a local Swedish boy's soccer team (again 15-16 year olds).
The fastest time ever by a woman 100m sprinter (which no woman has come close to in 30 years) is about the time of a fast 16 year old boy.
Or take tennis, one of the most lucrative women's sports, both Williams sisters lost badly (6-1 and 6-2) against the 203rd ranked male (who didn't warm up and just had a beer).
Basically the best women athletes in almost every physical (as opposed to something like archery or shooting) are on the level of a very good 16 year old boy. So ask yourself, are there any 16 year old boy's who could have won the first UFC?
Cyborg might be able to beat some of the guys who never grappled (assuming she didn't start off by striking with them), but she'd be far too weak and slow for the rest of them. Mind you, Cyborg would easily beat 95% of Sherdog posters and untrained men, but that's not what was in UFC 1.