You did not really ask any question here, so I will answer what I think the question is...
Would this be cool?
The answer is YES. It could be done as a CLOT, though I am not sure anyone has made a rotating template CLOT yet (I know it can be done though).
You could weight the templates based on votes and select one randomly with weights.
But, I'm not sure about your weighting process. How could you possibly check to see if someone has played X number of games on it? To do that, it would have to be the same exact template ID. Meaning, if you and I both have Strat ME 1v1 saved in our own template list with the same settings, they still have a different ID. If it were me, I'd skip the requirement of playing on a template as I'm sure we are talking about pretty main stream templates. You may be able to require games played on the MAP though, that would be possible I would think since that is already an open seat filter.
@ChrisCMU You are correct, the question is "Would/Should this be implemented/made as a CLOT". I'll edit that into the original post, maybe that is why this thread got no replies until you.
Also, I meant X games played on that template on that ladder. That should be a lot easier to check. Someone has made a rotating template CLOT, the Real-Time CLOT. The only major difference is templates would show up more/less often based on community approval.
^^ ChrisCMU's point is very important to consider. Fizzer needs to add a template query API that allows us to check for template settings (even basic ones would make it easier to track duplicates) and also get minimum levels without having to go through the DARKLORDS to get a player for each level from L18 to L56 (or something like that- I don't quite remember) and then query the validate token API with the template to determine which level the template requires for non-Members. Would also be useful to get what sort of unlockables (e.g., "CanUseBombCard") a template requires.
Another idea I had for a somewhat similar league- I wanted to make a more dynamic clan league-type setup with template flexibility where templates would be weighed differently based on how often they've been played. Would still run into the duplicate issue if I stuck with the CLOT framework, but you're already familiar with the workaround I'm working on so I'm not going to mention it by name until I actually release it. <_<