leave the name as it is, I can see you want it that way and its trivial anyways. buut to summon usually pertains to a someone, not a something. Evokers bring about things that aren't necessarily creatures - maybe that fits the bill?
im not sure this is the right thread. anyways you'll either need to make a model that has a skeleton below the ground or handle its movement by triggers. Or make fake water thats in the air out of those nice UTM water tiles.
Maybe combination units? Like you build 2 mechs and they can merge into a big stronger robot?
Or if your going for low technology, train big units like ogres/orcs that they merge and ride around - like the Alchemist
What if you just saved the sequence of buttons pressed? That way you wouldnt have to save each value and the coaster could load in the same way it was built. It might be a bit laggy to load, but it would take up a lot less space.