I'd run the logic in Low Voltage right on down to the motor -- which is where I'd place the dimmer.
Trying to stick the dimmer into the nearby box makes absolutely no sense to me.
As ever, the OP leaves me in the dark on all of the specifics that I'd use to really come up with a solution.
I can't tell if there are any wire running issues, etc. that'd prevent Plan A from coming off.
All I can say is that LV circuit logic and distant controllers is quite different now versus twenty-some years ago.
BTW, Cat 5 cable is massively displacing prior methods. If you can pull it in without grief -- it'd be my method.
There ARE controlers that can digitally multiplex on two-wires -- thence to decode at point B.
Lastly, be sure to isolate the LV switch logic from 120VAC. Such isolators are available from your e-distributor.