I like this idea... Too bad I can't figure out how to spawn add-on vehicles into a map. -_-
I didn't quite understand that? You mean you don't know how to spawn Add-On vehicles?
Well all it is is;
1) Place Vehicle Spawn.
2) Hit the brick with a Wrench.
3) Click on the drop down menu.
4) Select the Vehicle you want.
5) Click the send button.
You will also need the Add-Ons saved in your Add-Ons folder as .zip files, and will need them activated in the Add-On menu.
Sorry, if that is absolutely not what you meant, and just described something basic with no reason.