[Kipper]

Cool as they look, it would be silly to overpower them to the point of making them the only thing people want. Epic fights should include infantry, land and air all trying to fight each other.

One way to implement them would be to make an empire specific one that functions alongside the MBT; perhaps make one of the two faster, but weaker. Give one thing, take away another - essentially its a tank, but it just looks different - legs instead of tracks.

I'd could see a legged vehicle being well armoured and well armed, but intolerably slow, only spawnable from certain locations (or maybe 2 hexes inside friendly territory) and unable to ride in any other vehicle - so they take ages to bring to battle (primarily a defensive unit) and they are a sitting duck, but they can deal damage if you can get one up.

Or an alternative - make it jut like an MBT but deployable. Its the same speed and armament, roughly - but has a function to anchor itself and become a turret - whereby its immobile but has more firepower.