MapEditor ; NavMesh & Prefabs

Hello~

I’m pretty much new to Unity, and I use it to try to create a TowerDefense-ish game with my team. My job was to build a Map Editor, allowing the player to create his own road, putting pieces wherever he wants. This was a success! My teammate was working on the gameplay & co, and it was going OK for him too.
But the trouble started when we thought about joining our jobs.
I had to create a path associated with the pieces; he had no problem with his : he used a hard-setted road.
I’ve been looking for a week, and I found this :
http://forum.unity3d.com/threads/problem-with-navmesh-and-asynchronous-load.122545/
I really thought I had find my solution, but… no. If I understood well, it’s useful in the case of only one prefab to add.
In my case, I can succesfully bake one prefab, but the position is not saved, and I can use ONLYone prefab. Pretty useless, eh?

Considering this limitation exists for quite a long time, I was wondering if someone had a solution, or tips for my problem.

Thanks,

Anacho

PS: Sorry if I made mistakes, I’m not a natural english-speaker
PS2: I joined a screenshot of my scene “in-game”, so you can see what it looks like.

Up?
No solutions for me ? :cry: