Stacking Robots

[GeeTwo]

If you're going to coordinate this tightly, a "boulder brigade" should be able to speed up cycle times. One machine to round up boulders and deliver to the (probably tiny, definitely fast) courier 'bot under the low bar, which passes them off to the shooter. Picking up the courier 'bot would only be required to speed up breaching the defenses, and possibly the scale.

Scaling two robots in the time allotted sounds problematic. Although, if the lifting 'bot stayed under 4'6", it could hang the courier bot on a rung at any time. This would mean deployable hooks on the courier or hanging it sideways.