I replaced the demo trap for the GLA with the Iraqi Naval Yard, due to:
1) It won't effect the structure of the game
(it wont remove production structures)
2) It raises no scaffolding (scaffolding in water lol)
I made the building only buildable in water, and copied most of the code from the war factory in FactionBuilding.ini, however made the building only buildable in water. The code will become open source after the mod is released.
Currently I am using the one construction vehicle for every team, the hover construction vehicle:

However when beta comes all teams will have different construction vehicles, but all will be able to build in water.