That doesn't really work, though. If my fandom right now only has A/B nominated, my ship, that's great for me and there's no reason for me to nominate a second ship like A&B. However, I have no way of knowing what other people may still nominate. Someone might well nominate my NOTP B/C an hour before nominations close and I wouldn't know. Then the two nominated ships for that fandom would be A/B and B/C and I couldn't offer the fandom anymore. Someone whose only match might have been me writing A/B for them would not have a possible writer anymore, because I couldn't offer A/B without also having to offer B/C.
TLDR: Making it harder for people to offer the pairings they want to write makes matching harder, not easier.
no subject
participants could choose to nominate accordingly
That doesn't really work, though. If my fandom right now only has A/B nominated, my ship, that's great for me and there's no reason for me to nominate a second ship like A&B. However, I have no way of knowing what other people may still nominate. Someone might well nominate my NOTP B/C an hour before nominations close and I wouldn't know. Then the two nominated ships for that fandom would be A/B and B/C and I couldn't offer the fandom anymore. Someone whose only match might have been me writing A/B for them would not have a possible writer anymore, because I couldn't offer A/B without also having to offer B/C.
TLDR: Making it harder for people to offer the pairings they want to write makes matching harder, not easier.