I agree with you there; she probably wouldn't have fit into the melodrama that Melrose became. I loved when Jasmine Guy was briefly on the show in Season 3, and had they written it in such a way, they could've kept her character longterm or brought her back, just as they were able to bring Peter Burns back. I loved the tension between her and Amanda. I also liked Alycia Barnett (Anne-Marie Johnson) too.
I also agree they should've kept former characters "alive" by mentioning them more often. Even when Jo left after season 4, there was nary a mention of her again, not even by Jake.
When Rhonda left, I remember Matt mentions her in like the second or third episode of the new season. Otherwise, he mentions her one more time as he's recalling his time at Melrose when he leaves the series.
One thing Melrose was good at for the most part, though, was bringing back key parents of the main characters... Jane & Sydney's mom and dad, Billy's mom, Matt's mom and dad, Kimberly's mom, etc.