Scored approval voting takes care of ten candidates. And sure let’s say after 3 elections with no winner fines could be imposed too, Australia style. But I would hope that having no representation while having the opportunity to have representation would be motivation enough.
there is no "scored approval voting". approval voting is literally score voting with a 0-1 binary score scale, and with the scores implicit in the state of an empty or filled oval.
And what if there are, say, ten candidates?