Hello.  Is it possible to make Scientist walk on player's foundation? So I can build a scientist military base for players to raid. (with RaidableBases)

I think not. Someone may correct me later but, if I remember correctly, the NPC navigation meshes do not include dynamic structures yet.

You could see what you could do with Human NPC (https://umod.org/plugins/human-npc) and Path Finding (https://umod.org/plugins/path-finding).

Building foundations have a component called AI.NavMeshObstacle that keeps out the AI.  If you remove it, they may be able to clip through buildings.  To get them to walk on buildings is probably much harder. 

When CustomAnimalSpawns plugin and RadTownAnimal spawns first came out i tried to spawn the animals and zombies inside caves and monuments to no avail, the same with Botspawn, they would sometimes spawn on top of a roof but not very often,
My *guess is that after all the complaints FP got when they (re)introduced wolves and bears into experimental rust and the animals would walk through base walls they found a way to constrain them, If you remove the AI.NavMeshObstacle would that also allow other animals to enter structures that you dont want ?

I used a plugin to make some buildings without foundations.  Walls, floors, doors, etc.  They made for good traps.  Players would walk inside and think they were safe.  Then the zombies and bears would clip through the walls and get them.