Not sure if its exactly relevant, but I would also add From the Depths as well. It has a very steep learning cliff, but once you learn it you can build all kin

Not sure if its exactly relevant, but I would also add From the Depths as well. It has a very steep learning cliff, but once you learn it you can build all kinds of war machines, from ships to robot walkers and spacecraft. And you create the individual systems which your vehicles use as well, such as steam engines, weapon systems, AI, etc. Its a game I've spent many hours in.