It would be really useful to improve performance (especially on mobile) if you could select groups of entities that could be baked into a static mesh or meshes. The way this would work is that the selected objects would be grouped by material and then baked into the minimum number of meshes (based on the number of vertices, this might be more than one).
The baked meshes would then be used in place of the individual meshes at run time. This can even be done with objects that move (though not ones that are added or removed at run time - for which you need pooling) as they can be created as skinned meshes and this still significantly reduces the overhead of the extra draw calls and a whole bunch of positioning logic which is wasted when these items will remain static.
This feature is a more advanced version of Unity's static mesh stuff.