I can definitely understand the flailyness of losing important IC relationships. There was even a time when I (briefly) considered retiring Lilly post-gunslingers because I didn't see how I could keep playing her without that group of people. Obviously I didn't, but it was a rough time. There have been times since then when an important group's gone quiet or retired or whatever, and they're not always fun to play through. And there are those times when for whatever reason, one half of a couple disappears and while that sucks, it is possible to find ways around it, like Heater's done with Alanna.

I think what it comes down to is if you're willing, interested and able to do 'pretty much anything' and you put a lot of time and effort into maintaining IC relationships and creating new ones, then you'll find new references and ways to stay playable. As far as replaceable/redundant relationships, I'm not sure I understand what you mean. Given the people you generally play with, I doubt any of them are trying to make you feel either replaceable or redundant even if their pup's circle has expanded while yours has contracted.

It's up to you, of course, to make the decision about how much you want to invest in finding ways to keep Crowley playable as well as how much time and mental energy you have to invest. It's a tough call, so good luck with that.