Re: Best karate style for aikido?
I am also doing Aikikai Aikido and Shotokan, and I enjoy both. I donīt know enough to pontificate about cross-training in general, but I can say for sure that it would be a good thing for Aikido students to have at least some basic Karate Kihon training so that they actually can through a punch. (Likewise, I find that some people at Karate place look ridiculous in the occasional situation where they have to take a fall.)
Going back to the original poster, if he is interested in mixing the arts maybe he find a Yoseikan Budo place? That would seem tailor-made for him. Both Karate and Aikido, combined in a systematic way as I understand.