If they are all using the same material, then I think you would be able to use Blueprints to make them all one draw call. Or, it might be better to just export it all as one in the first place, depending on what your needs are for it. It sounds like you have some advanced technical skill in 3ds Max so maybe you could have it automatically optimize a whole build and make the LOD’s for it to export to UE4. My guess is that you’ll probably end up with something that’s less optimized than doing things by hand, but you might be able to get close.