Maybe the virtual trainer can be something that is client side-only.
This isn't a simple change by any means, but to elaborate:
The client PC already has all the graphical information, so while in training mode, when the user deployes to the terrain, they don't actually enter the persistant Perp world server, just a client-side representation of the world. This is different from instancing, its more like an 'offline' mode, except that the client would still need to be authenitated to the server and the client-mode initiated.
As long as there was no reverse synch, anything that happens in the client-mode wouldn't be updated to the persistant server.
Of course, in addition to the client code changes, you would also have to add offline 'content modules' that can simulate ore and NPC's that would normally be server-side info.
- This doesn't allow for trainers to join in, but that is something that can and maybe should be done on the live server anyway (Various reasons for and against multiuser training, but nothing that would be a serious argument one way or the other).