From a rappelling exercise I did a long, long time ago, I know that you can rappel down a knotted rope without losing speed and without falling off when you hit the knot, using a rotating zip-climber that mechanically rotates itself around the knot without allowing a cantilever on the part of the climber.
Such a device is feasible for an FRC robot on the corner post -- clamp it on and power it, and then just drive up! (You'd go to half power over the knuckles -- compensated by momentum but detracted by gravity -- but full power elsewhere).
What it isn't is possible for 1551 to properly develop and test over a six-week period.
