Semi Dynamic Shadows

I completely understand that you can bake shadows for you're scene that don't move and I do that for surrounding things that dont move. But i am loading my scene at runtime via instantiate. With an rts the user loads their map by logging in and it places multiple object on a grid. The grid is 50x50. So their could be up to 2,500 dynamic objects on the scene that hardly move.

I'm not wondering how lightmapping works. I'm completely aware of the concepts of it and what i can and cannot do.

What i'm wanting to know if there is a way to extend it like so.

The game is loaded. The map is loaded via instantiate ( however the user has designed their map). When loading (or when user moves something on their map)-> Render dynamic lighting to texture on the first frame. Use that map again in subsequent frames without recalculating it every single frame I hope this is a little more clear on what im looking for