although I'm not working with a team this year (reffing at Peachtree) I have given some thought to a simple climbing device. It would allow for relatively simple removal as well. I'll have to make some sketches of it tomorrow and post it up here
I'll give a quick shot at explaining it though.
Picture a wheel, it has no hub, but is still driven. (This can be done) Now imagine it has "fingers" coming off of it, kind of like hooks that would hold the corner of the tower and push it against the wheel. These fingers would alternate which side they held the tower from (left, right, left, etc) and would connect and disconnect by a cam that would push them out (to allow it around the tower corner pole) and then spring force, or surgical tubing, etc. would snap it back, pinching it to the wheel. As the wheel rotates, it simply drives right up the tower, each of its little sloth fingers holding it in place.
Of course this idea isn't remotely fleshed out and would need something like skids to keep the robot from slipping and rotating around (unless that was all part of the plan!), but that is my attempt at relatively simple and reliable