You dont need a capstan with a powered winch takeup. I assume you are designing the winch that self-locks.

Who ever is asking the question does not fully understand the design principles.

The winch would have to be active during a power-loss stop. This would require unecessary and oversized winch power for it to act as though it had the speed of gravity.

Normally, a winch is locked during the stop and therefore acts as a fixed take-up. If not locked, it would be very slow wrt the take-up response and would again seem to be fixed in time.

Often the purpose of the capstan is to fully or partial boost the take-up level to control/limit undersirable pay-out of the take-up motion, which in turn feeds a low tension (high sag) area somewhere along the belt loop, or limits the deceleration action of the head/drive system to control a shock wave problem. ■

On second read:

You note the winch is not automatic. This means it is manual. If manual, it is self-locking. When self-locking, it means it is fixed. Capstan has no function when self-locking. ■