Currently no hack supports having more than one, though it is definitely a good idea.

As I understand it, the game can only have one free vehicle spawn trigger active *at once*. You can have multiple per level, but you'd need to not put them in the TERRA file and instead use dyna-loaded region files. Even doing that only one region can have a free vehicle at once so that region needs to be unloaded before any others will work.

How are you supposed to even play this mod if the mod doesn't even let you apply it's dependency (Colou's Fully Connected Map mod)?

The necessary files for the Fully Connected Map are contained within this mod, as with any other mod that uses it. You don't enable both the mod and the Fully Connected Map at the same time, just the mod.