There would be as many candidates for each party as there are seats to be filled in the constituency. We can imagine that a party would have the right to present fewer candidates. I don’t think it's a good idea, but I would have to think about it. That might create distortions.
In a proportional system, political parties usually prepare a list of candidates equal to the number of seats in the constituency. That's what probably should be done. If you want to run candidates in a constituency with three seats, you will have to submit three. You have to make a list of three, four or five candidates, depending on the size of the constituency.