Both Spike and Faith are pretty much shippable with ANY other character, IMO. They do have a lot of emotional issues in common, it's true, but I don't see that as an impediment to them being good together. Faith is to Buffy as Spike is to Angel, in a lot of ways, and it would help both of them to have somebody for whom they are the primary focus, after being in the shadow of others for so long. Plus, they could indulge in mischief while those around them played the dour and serious roles.

If you are looking for fic, try the Spike/Faith tag on justrewards.com. Everything by anaross is great!