I think PR-STV could work, even if I'd need a crash course on how to calculate it.
Another option would be to do a straight up Yes or No vote to endorse each candidate with a certain percent of the vote needed to endorse.
That's probably a better idea. It'd be the easiest system to work with for endorsements, IMO.
I'd be supportive of that. It would be much easier to calculate.
STV Quota
Votes needed to win = (valid votes Cast/seats to fill +1) + 1
Avoid the problems made by transferring overvotes by simply transferring votes by order of votes cast