Yes. I already mentioned this idea to place several entities at once.

Your hmp tools look amazing from what I can see so far. From my point of view a possibility to paint textures directly ingame would be great.

I mean: You could support a special kind of a multitexturing shader. The textures for grass, stones, rocks and so on have to be added to the hmp. There is an external bitmap for the blending (maybe with alpha channel or with RGB channels) and we simply paint in this blending map with the pencils that you provide in your editor.