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Team update 1 shows that the only form of energy storage allowed on the minibot is the battery, and the only way you're allowed to convert it to mechanical energy is using the motors.
Sigh... but at least the rules don't (yet) require you to use the Lego controller or speed controller for the motors... in fact I see nothing in the rules saying that the motors need to be turned off at the start of the match, either.
So having wheels clamp on and climb sounds like a pretty good technique.
Jason