That makes sense. I don't really view L as sexual, either. He could have sex, that wouldn't be that shocking, but I don't think he's the type to seduce people or start flirting heavily.
Despite my more romantic inclinations, I believe that anything between L and Light was volatile and unplanned. Any love that existed was based on a feeling of mutual understanding, rather than hots for either's looks or personality. In other words, I think they loved each other because they understood each other, and both craved to be understood rather than simply regarded as machines to solve cases (L) or represent a limited social role (Raito as the 'good son.')
That said, I think any sex would have been unplanned and selfish, rather than your typical erotic lovefest (though my romantic side loves the latter idea better, even if it's unrealistic!)
I think, if L would have defeated Raito and sent him off to prison/death row, he'd feel like a part of himself was dragged away as well (so it would be a selfish sadness, rather than pity for Raito getting the justice he deserved.)