Let's get right to it.
I was thinking that if you could place blocks in such a way that it spawns a vehicle (think building an iron golem in Minecraft.)
Say, you build a jeep shaped structure, a jeep pops up.
Different shapes spawn different things, and you will have to memorize how to build anything if you want to build it, just like you have to memorize the shape of a Nether portal.
This can provide a whole new role players can take while in the battlefield. Some men are fighting while the others are building vehicles.
I was thinking you could also build useful objects like timebombs or something, but I'm not quite sure how that would work.