Oh there's nothing wrong with Kazuma—funny, his own brand of intelligence either in battle or just life, gentleman to balance his brutish side, has good endurance, love of kittens, strength to hold his own against demons... and I think he's attractive when he's not making those comical and outrageous faces. And even those bizarre faces don't disgust me... they make me laugh.
A lot of girls seemed to like him in high school, but I think they were mere fangirls and thus would have to be the dreaded OCs/Merisus. Of the canon girls (minus his sister for obvious reasons) Botan or Yukina could work. Botan doesn't seem interested and it doesn't look like Kazuma's soon to pick up on her again. Yukina, though she likes humans and I don't see her as innocent as everyone, I don't get the sense that she feels the same way either culturally or emotionally founded.
Pairing him with guys is hard since he's a bit uncomfortable with guys in that manner. He seemed pretty disturbed by that dream where he kissed Yusuke. Then there was when Itsuki mentioned he loved Sensui and Kazuma was again, irked. Oh and let's not forget when Kazuma and Kurama were waiting for the train, two girls from Kazuma's high school said "Oh we didn't know about this side of your life" after being corrected on Kurama's gender. He was pretty mad. Also, I think I remember him being pretty pissed when Botan said something about it being strange for two men to watch the sunset together.
Ultimately those things can be written but it takes a good author, an accepting audience and fans of the character in question.