Seems like a bit of a solution waiting for a problem.

Given the current limitations in the system I would go with a monster battler game with a starter set of just 2 cards which would be yours and your opponents monster and then add a selection of power-ups/abilities these could be much cheaper components that could be played on the base station for an effect. These could be swipe cards or even just resistors basically anything that can be measured by the base station. With this hybrid system you could get the cool evolving over time monsters as well as lots of pieces to play with. Lots of scope for cool and hidden interactions. (Ideas taken from digimon tamers)