I'd think that a theme team has to reasonably be some kind of small minority to be picking from. Allowing a team that can be picked from ~50% of the world's population doesn't seem particularly on.
But, it depends whether the theme team league is a "fun" thing or a competitive thing.
Let's get statistical and weight teams based on the percentage of the overall population that their team consists of. Therefore, a hit in the "all male" or "all woman" team might be weighted at 0.5 based on women/men being approx. 50% of the population. Then, on the other hand, selecting a team from the cast and crew of the 70s film for masochistic children, Watership Down (like my better half did a couple of years back) would afford each hit a weighting of ~100/7.5bn. So, if Ray Merrin had received a QO, then he'd have been worth the standard number of points divided by (100/7.5x10^9) which would have meant Merrin would have scored ~3*10^8 points for her (300,000,000) compared to only 8 points for the hypothetical person selecting Merrin for their all male theme team.
I think we can all agree that the simplicity and satisfaction in appropriately awarding niche teams would go a long way towards making the Theme Team League a more highly respected competition.