Very few conferences in any division use something other than a tournament. The Ivy used to not have a tournament in basketball for their AQ selection (they were the last to not have a playoff).
If a majority of the the schools in the UCHC wanted to use that method they could change their rules.
I don't particularly like one-and-done format playoffs, but again that is the choice that has been made. I'd rather see some kind of series format but most leagues don't use that. The situation is not unique to DIII hockey. Could it be changed? Lobby your conference for a change. That is how it can happen. It doesn't come from the NCAA, but from the conferences.