Given the Yard Mule is easily the biggest selling plan why not design a power take off system for it similar to the early Land Rover. This could then power a range of other attachments which could then be the subject of other plans such as a circular saw table, winch or towed mower.
Or equally how about a plan to construct a wind or water driven charger for it's batteries.

Or equally how about a plan to construct a wind or water driven charger for it's batteries.