Hi mercuryus!
Seed_it as I already told is very good, but to make it work you need to assign an action to the terrain/model, my question is that I use the mdlterrainmulty
action for multitexturing my terrain, and as you know we could use only one action pro model (unfortunately!) My ideas is to use one copy from the terrain
put it in the level use it for crate the plants, stone and grass save all the model position ,their actions and their property, delete the second terrain copy
and use only the models in your terrain level.

Greet
Salva