[DonRotolo]

See all the above first.

Next, you should consider some kind of winch system. The smaller the 'spool' the greater the mechanical advantage, while larger spools will wind more material per rotation.

With a winch you want to prevent back-driving, the tendency for the weight to let the spool unwind when unpowered. But remember you need to be able to get the robot down, eventually.

The 'rope' you use needs to be more than 2x as strong as necessary. A 300 lb breaking strength is not, in my own opinon, safe enough.

Look up the term 'fairlead' as it applies to winches, and consider using one.

Lastly, remember that if your robot turns sideways (wheels against the tower), your 'hook' will be more than 15" outside your frame perimeter, which is a problem.

Good luck!