So, some very sad news for me and then some good news for you:
Despite being led to believe that custom props and the like would work ingame, I got to the end of the project only to learn they can not be used.
This includes the trees and the custom gate model that I spent a rather large amount of time on, so i'm actually pretty bummed out about that, lost all my motivation to work on the map and all that stuff.

That's a screenshot of the FAF editor, with the custom assets.
Here is the same area, but with the "standard" solution.

As you can see, the textures still work fine though.
The good news is that i'm uploading this map now because it is done, and I don't have a reason to keep it from you any longer.
The map name is Gateway and Rose and supports 1v1 through 4v4.
The name is a take on the Torii gates, and the overall map image looking a bit like a flower, as well as the pink trees that were also present.
I already did a large amount of tests to check if the mexes can be raided by frigates, so they can. There is also a civ AA on the top level that discourages dropping the other side of the map.
Here is a strategic view of the map.

It's really annoying to update this map because of the texture file paths, but i'll be watching replays and pushing and changes if I need to do that.
(The release version is v2 because of the above reason)
If the option to add custom props ever comes available in the future, I have the version with the assets on my machine, so maybe some day...
I want to make a teamgame map next, but hopefully you'll understand that my will to do so is rather shot after all of this.