i have not worked with the BF engine, but i have worked alot with the unreal engine. they seem to be similer, minus the "bsp" portion.
the engine only needs to render a object (static mesh) one time no matter how many times its placed in the map,...get too many unique objects and your going to be taking away fps. That is probably the reason for the many "copy" buildings. There are a good number of unique buildings in bf42, (not alot) but they are just not all slammed onto one map, and i bet that has more to do with rendering than "design".
I would love to start seeing more buildings you will be using in the mod instead of just vehicles and the occasional weapon. Let us see that lighthouse when it is ingame and skinned. :agreed: