Re: cross training options
I don't know what's available to you, TS, but I'll stick to taekwondo and kendo here since that's what you put in your post.
There is a lot of bad, commercialized taekwondo out there. If you're going to do TKD, make sure you find a good school. TKD is a great cardio workout, and will build flexibility and balance: all good stuff for aikido. Many schools, though, will devote disproportionate amounts of time to high, acrobatic kicks which aren't much martial use and won't serve you well in aikido. If you find a good instructor (preferrably one with experience in other martial arts who doesn't buy into the Korean nationalistic nonsense), it can be a good addiiton. I have done some crosstraining in TKD.
I have no firsthand experience with kendo, but I have known many aikido people who say learning more about the sword has improved their aikido.