hm, that interesting throughs
what Ihave to say
1) Normally, stomp is last resort weapon. When you have no range 1 weapons and enemy is close, or when you have no energy - stomp help you, and thus shouldn't put any cost here. However, there is an exception: specific myphical legs with 2 uses and huge damage, in that cases stomp is not last resort measure but additional weapon you can put into "legs" slot. That legs' stomp could have some cost, as you won't be able to use it many times anyway.
2) Original BattleMechs had jetpack. You travelled 250% distance, but used 13 energy instead of 5 to walk (yes walking used to cost energy back there; no it basically affected nothing). While "legs" walking normally consumes nothing (and, as we have alot of energy drainer weapons, I think it should stay as such for 1-tile moves), long movement could have some cost. Like, if legs can walk for 2 or jump for 3, jump would cost few energy, so fully drained mech still can walk for 2 but can't jump so good.