for aikido, the rowing exercises and various Tohei's aiki taiso exercises would work, as long as you initiate all the movement using the one point/ball and breathing, kokyu remember?
Which is very hard when you are first working on it. I mean, I've been doing those exercises for years, but was doing them with center and one point essentially as metaphor for center as in pelvis/hips.(Being told to "Imagine a ball of energy" is a totally different instruction than being told to/how to isolate and work that circle!)
Anyhow.... I'm finding that it is essential to work on this at home as in class we only do say 8-10 reps of each exercise and it takes me that many to first get my one point moving the way I want, then get it to move my largest adjacent joints...by the time I am ready to add in my arms, we've moved on to the next exercise. At this point, If I start right in with including my arms, I never get the one point properly engaged.
My 2 cents, may not be worth that much