Anyone try this?

There's no system nor presentation that I know of and - obviously - the legs have less rotational freedom than arms. And you'd have to be careful to not twist (injure) the joints of your rooted leg. But... Fun idea to experiment with.

i've thought about it....

however i don't think it's really applicable to humans.

the clubs work for CST as our hands are designed to hold and move weight.
if you could hold a weight with your foot (i can hold a soccer ball with my foot ) then.... perhaps you could work this way and get the same kind of training effect.

however our legs are designed to hold our structure upright, in that sense best circular strengthening exercises for the legs would be ones that utilise the weight of our own structure.

for that you can't get any better than "body-flow" exercises! as well as things like the 4 corner balance drill, trinity squats, etc.

there are also clubbell exercises that become a lot more lower body orientated (although every clubbell exercise will utlise the legs to some extent as two of the 7 principles are leg drive and hip recruitment) such as adding lunges, squats or side-steps as well as things like rockits.

just my opinion only here.