For any counter-wobble system remember that some sort of energy input was needed to induce the wobble, and that has to be counteracted, not just stopped.
The energy input in this case is the docking of a starship [SS] in the hub, massive and off center.
OK, I didn’t see that now you are intending a Starship to enter into your station, like adding a bullet into a six-shooter.
That opens up a whole nother can of worms about how that is supposed to work, but I’ll ignore that to focus on the balance discussion.
Here is what I don’t understand about your concern with docking a large visiting vehicle at the center of rotation for your station – where is the force coming from that is causing a wobble? There is no lever arm at the center of rotation, so at most the large visiting vehicle it just pushing the station sideways with the docking force. But if you are docking slowly, that amount of force is going to be minuscule compared to the total mass of the station. People walking in the 1G section of the station have a 100m lever arm, but the visiting vehicle has little to none.
Once the starship is attached to the R/S the station would be off balance. The water mechanism is intended to balance the off-center mass. As the SS unloads, the rebalancing effort must continue. This is a good reason to prefer water as the rebalancing medium over the mass elevator proposal. There is a short lever arm at the docking hub coupled with the large mass of the SS itself.
For weight and balance, yes moving water around is one method.
Though looking at the scale on your drawing I find it hard to believe that the tiny Starship that is located very close to the center of rotation will shift the center of rotation enough to worry about. Just look at all the mass you have in the rim compared to the mass of the Starship!
Also, shifting water won’t correct wobble, but I know you plan to have an RCS, however what happens if you run out of propellant?
Which is a valid question for all rotating space station designs, not just yours. which is why I’m looking into a semi-passive system that may be able to dampen wobble, though it may not be able to correct rotation orientation post-wobble. Certainly points to a need for a full physics model for us to play with…