I agree with what you said about it feeling Faith was rushed in Season 7 but at least they showed you Faith & Buffy becoming friends again.
And Faith agreed with Buffy that it wasn't just the fact that they were both Slayers that made them rivals but her mental state as well .
True, I also liked her scene with Spike. Her and Spike would have been a very interesting couple I think, though obviously it was too late in the day to bring that in.
I often wish Spike and Faith had got their own show after S4 of Buffy. To me they were too big characters to just be side characters in other series.
I can see Spike skipping town after S4 to escape the Initiative, whilst Faith had left after Angel s1, and the two of them ended up in a small town together. The Slayer/Vampire romance would have been a better fir for those two for the following reasons.
We wouldn't have to rewrite Spike's past. Also I totally buy Faith being attracted to Spike and the fact that he is evil. Again with Buffy that just came out of nowhere and we had to rewrite her past to be, she was attracted to Angelus, or at least the fact that he could be Angelus, Buffy likes it rough UGH, I hated all that. I agree with Sarah it was demeaning to her character.
With Faith and Spike we could have got all the good things about Spuffy, like Spike becoming a better man, crazy Vampire/Slayer sex, but without the baggage.
Again though I suspect a few people will disagree with me on that, but that's how I feel.