I get the impression from the top post that that system isn’t exactly what they’re looking for.
The issue with the Wayhaven system is that it either removes player agency or character agency–in the case of Wayhaven, player agency, as the main character has to be basically a good person. Which isn’t necessarily a negative–I really enjoy that series and it’s characters a lot–but if the main character weren’t limited in scope, then having a system like that could make ROs feel like they don’t have their own say in relationships. If the MC of the Wayhaven Chronicles could want to murder every single new supernatural they come across but like, still get to fall in love and have a completely perfect eternal love with one of the vampire ROs, that would feel really really off. The rel stat system isn’t perfect, but it does give ROs some agency–if they can reject a character who’s done enough things that they don’t like, the relationship can feel more earned and natural. (It doesn’t feel unnatural in Wayhaven, but–as per the author’s own admission and goals–the story is railroaded in order to service that. It’s not an inherently bad thing, but it is unique to that story and won’t work in every game.)
It seems like the question of balance more or less boils down to “how low can rel be before it should have negative impacts on the in-game relationship,” which should really vary between game and game, and character and character. There’s not a one-size-fits-all answer for what the hard rejection line should be.
And there are some romances that are really hard to get, for good reason–sometimes an RO is just really picky and would only realistically be attracted to a specific type of character. Personally, I agree that I prefer ROs that have more intuitive romance paths, or at least less strict ones, but if it’s designed to be intentionally difficult I don’t think that’s strictly a bad thing