I have been building objects in Rhino and having good luck importing them to scale. I draw the objects doors etc. to fit a 6 foot avitar. I make a big sphere with up to a 1000 ft radius around the objects. I import to blender with the clamp scale set to the same size as the sphere. This can be dragged to where I want it then deselected. If I reselect the sphere and delete it I can drop a building with all the textures and scales set for the game. I've done three or four with scales and my avitar always matches the 6 ft scales I build with the meshes.
I have a couple of problems with this method. The clamp scale in blender has a 1000ft max. Is there any way to increase this if I want to do an entire age larger than 1000ft?
I have tried mapping schemes not available in blender. PNG textures work great but BMP textures were half transparent. What textures can I use that work in blender and the game?