I'm all for cross training. I've practiced iaido almost as long as aikido - although not as much.
Maybe it's important to be consistent with what is one's major in the martial arts. Otherwise there is a risk of getting more confused than skilled. Also, from the
perspective, knowing one's major path is quite essential.
I also discourage complete beginners from trying to learn more than one martial art simultaneously. That would make it hard for them to find some clarity, and to pass the beginner phase.
Other than that - go for it! Actually, it's essential to become familiar with other martial arts in order to properly understand how to attack correctly as uke.