It's not as easy as it should be, but try this...
Make your farp / base out of the real thing as desired... Then place a vehicle group over the top of what you have laid down with the exact same orientation as the statics and save that vehicle group as a template.
Whenever you need that base in the future, place the vehicle template and then reverse the process above.
It's not quick or elegant, but it's a lot quicker than creating from scratch every time.
Here is one made up from a couple of my own and some from the community, sorry to the authors, but I can't remember who to credit for them!
Please note that there are a couple in there that use Beczl's vehicle pack, so unless you use that pack (and if you do and use those vehicles in mission, the people that fly it use them), you won't see them.