Sano x Kaoru could probably work if not for Kenshin and Megumi's existence.  They look good together and I like their height difference (kinda reminds me of Tamahome and Miaka of Fushigi Yuugi).  They also have quite a number of things in common.  They're both young, fiercely loyal to the ones they love, and basically easygoing (not brooding and intense).  They are friends, which could probably be a good starting point of a romance.  But since, Kenshin and Megumi do exist in the manga and anime, I guess it's better for the Roosterhead and Jo-chan to just remain friends.

Soujiro and Kaoru?  Hmmm, let me think...  In both the anime and manga, they never got to meet each other at all so I can't say anything about their interaction.  But sometimes, when Kenshin is being an idiotic blockhead, I wish that the two of them do meet.  Wouldn't it be cool if Kaoru and Soujiro actually meet and fall in love?  They look so cute together and I think that someone like Kaoru is just the girl Soujiro needs.  I'll bet that if he did meet a Kaoru-type girl (complete with her own dojo), he'd stop wandering too like Kenshin.  Mind you, I don't have anything against K&K.  I love the 2 of them together, but in some instances (like in the engagement ring filler episode), I want Kenshin to have a rival for Kaoru's heart so that he would learn not to take her love for granted.  Anyway, if not for Kenshin, Soujiro would be my top pick for Kaoru's leading man.  But since Kenshin does exist then I guess Soujiro would have to be content with having ME as his girl (bwahahaha!!!)

Aoshi?  Now where did this come from?  Actually, I never really thought of Aoshi as a possible match for Kaoru.  I've always thought that Kaoru went with Kenshin (or sometimes Enishi) and Aoshi went with Misao.  Until I read this fic by Sakka-chan.  It was so beautifully written (I'm ashamed to admit that I actually cried all the way through it!  Hey, what can I say?  I'm a real softie!) and the characterization was quite good.  It made me see Kaoru x Aoshi in a new light.  Now that I think about it.... well, they could work out as a couple if:

a) Kaoru learns how to cook, or at least learn to make a proper tea.

b) Kaoru learns to control her temper

c) Aoshi learns to loosen up, even just a bit.

d) Aoshi learns to do the laundry.

and...

d) Kenshin's dead. ^_^

Enishi x Kaoru : Everyone's fave alternative couple.  To be honest, I've always been intrigued by the possibility of Kaoru x Enishi match.  They look good together (See picture below) but I don't think it could work out.  For one thing, Kaoru's just too in love with Kenshin and another, Enishi is just too obsessed with Tomoe to want to deal with anything else.  But if ever they do get over their afflictions, it could probably work.  Kaoru is the type of girl who could steer Enishi from his psychopathic inclinations and be his sunshine.  Enishi on the other hand could.... Geez what could he do for Kaoru???  Nothing I guess.

    P.S.  Just a thought... who do you think changed Kaoru's clothes when Enishi brought her to the island?  She was wearing her practice clothes when Enishi kidnapped her and when she woke up, she was already wearing this bathrobe (?).  Probably, it was Enishi who did change her clothes... I wonder what he was thinking while he was doing so... -_~X