I personally can't see Ichigo as anything other than a bottom. I'm not really sure why, I think it’s because he acts like a bad ass so much in the show that I love seeing someone dominate him so much. It doesn't matter who it is.
I mean, imagine the hot, rough, angry GrimmIchi sex! Grimmjow pounding into Ichgo’s tight ass, and Ichi just screaming his name… I just… I can’t. (Man, I’m a yaoi junkie…) At this point I don’t think I could see Ichigo as anything other than a bottom. I’m such a nerd XD