The assumption that storing values above *.maxvel in a movement sysvar wastes nrg is incorrect. It is a general rule in the simulator that bots only get charged for the resultant action, not the action attempted. The simualtor code limits the magnitude of the vector sum of the bot attempted accelerations and thus the action portion of the cost equation to the max velocity (which then gets multiplied by the movement cost and the cost multiplier to determine the actual cost). Bottom line, bots storing huge values in movement sysvars are not charged more than that needed to accelerate to maxvel.
I should also point out here that there is a hard limit on voluntary movement costs, restricting them to values between -100 and 100 (costs can be negative if the cost multiplier is negative). This limit is very old code. It predates the cost multiplier. No matter what the result of the cost calculation above, no matter how high the cost multipler or the user-specified movement cost, the actual cost applied is capped at 100.
I would very much like to remove this restriction if there are no objections. It is one of the few places where costs have a hard cap. It is also one of the few places where the will of the cost multiplier is overridden.