A character type that can work even better than a bofriend/girlfriend is to use a "Ducky".  I refer to Jon Cryer's character in "Pretty in Pink". 

Although not a perfect fit: Cryer's character is well-known enough to illustrate the point. -- I like the idea of a loyal character secretly pining after the Heroine enough to help her to make her dream come true even if it means that his dream will not.  The Geek/Nerd who helps his friend get the school heartthrob even though he would love to have her notice him instead. 
Of course in my version the girl would eventually come to her senses and choose the Ducky in the end.

Tschuss!
Hunter

Not quite sure how you mean, although I agree with your sentiment that BF/GF characters ought to provide more than gratuitous sex.  Do you mean it would be interesting to have a character gain a SO while literally going hrough the whole clothes-ripping process?  Or just more generally while learning to cope with an increasingly fragile world in a more long-term story, over a period of days, weeks, or even months?