Buffy/Spike, platonic partnership

Vague idea for a post-show fic I will probably never write (note that I do not read comics or consider them canon, so I am just thinking in terms of show canon here):

What if Buffy and Spike decided to have a relationship/partnership that was romantic, but not sexual? That after the events of Seeing Red, Buffy could not find it in herself to enjoy sex with Spike, but they still wanted a relationship? Maybe an open relationship, where they might have other boyfriends/girlfriends on the side with whom they did have sexual relations.