Re: It's (not?) all in the hips
Also, you could start throwing people down to the ground instead of away from your center (I'm making an assumption here based on what most Aikidoka do). That way you wont have to use your hips as much to project a person into the air; instead, build a false base under Uke and just let the throw and gravity do all the work for you.
Take the motion for a sword cut for example. Your hands are moving away from you at first and then once they reach their full extension they start to arc back towards your center...basically making a half circle in the air. That is the basis for most of the throws in certain styles of Aikido and are present in Shiho-Nage, Kotegaeshi, Sankyo, Ude-Kime Nage, etc.....
But if you raise your hand and just drop it from the elbow first and then let your hand fall (so your elbow is moving faster than your hand) like the common "trucker horn" sign, throws become more centripital and the arm motion becomes more whip-like. Rather than centrifugal and away from your center. When you project Uke away from you in any throw or technique you need to use your hips to compensate for your loss in power and ability to control Uke.
Of course using your hips will help in both situations, but you can also start using power from your legs as well and then power from your feet and then power from the ground and then all at once. Then make every thing you do centripital and constantly drilling down into the ground and every movement will become a manifestation of power and you will actually be powerful rather than having to generate power. There is a difference between the two.
Just my .02 cents