Ok, first off i don't know much about modding, but as i see it there is only one way to get something the way you want it, do it yourself!

So before i start asking the questions, i want to give a basic idea on what i want to do. For years i have had a love of capital ship combat, more specifically WWII stuff. I want to have a similar set up where capital ships lvl up and you actually want to take care of then as they are valuable assets, not just a throw away job.

So i would like to do a complete mod of the game over to a WWII naval game. Changing planets to islands, the area around a 'planet/island' is the combat zone, resources change from metal/crystal to metal/oil, ships to appropriate ship classes for a few diff countries. The main problems i foresee will be the ships moving off from the one plane and also building on the wrong plane. 

Questions

Is there a way to disable the ability to place buildings on different heights?

Is there a way to disable ships from using the z axis but still leave it open to aircraft?

Is there a way to do the above, but for the aircraft to only operate in + z axis?

Feedback appreciated, but please don't say 'use this game instread' or 'just play blah blah'. All I'm asking for now is if the game mechanics would support these ideas. I have thought of other mechanics in the game plus balancing the units and that sort of stuff.