I agree with basically everything you said.
I liked Cander, but because Xander was immature and can not let himself be happy with what he has, he goes and f*cks it up. I think their relationship was good for Cordy and that she grew as a person while dating him. But personally, I think that Cordelia loved Xander more than he loved her.
Ceasley seemed like it was just a way to get Cordelia involved with the scoobies again. It had the plus side of letting Cordy move on from Xander, adding more humor with Weasley's character and letting us know that Xander still had feelings for Cordelia. Other than that there was no reason that they would ever be together. Which is why it didn't last more than half a season.
Coyle would have been interesting to see. Cordy was still fun and had some bitchy tendencies but she was also a good person, a relationship with Doyle would probably been a better path for her than the one she got.
Cangle was stupid. Sorry, but I can't understand Angel falling for her after seeing his disinterest in her on Buffy. As well, Cordy was really angry with Buffy after learning that Angel was back in season 3, and we never saw her fear of Angel resolved. Finally, Buffy was Angel's soulmate. End of story. It would never work with anyone else. Angel and Cordy only got together because the show needed a romance with the lead character and at the time Cordy was the only option.
Cordelinor never should have happened! By this time I was already disappointed with how Cordelia's character had changed. I don't care if their relationship was the product of a demon it was sick and wrong and a disgrace to Cordelia. I would have been fine with Connor having an innocent crush on Cordelia but it went way too far.