It is nice to know, that you are working hard on this (and the others too, of course), so hopefully it will be a sucsess in the future.
But I also have some suggestions too.
Here is something that I just found out:

Could you make it so, that one can place NPCs at slopes too (at the red marked ares on the pic), so one dosn't need to hide the default-layer and re-show it , after placing the NPC?
How it is now, it is complicated to do, in my opinion.
Also, when you place an NPC, where you put an event in junction with, and you change to another NPC, it still has the event junctioned, which led to several problems and extra work, in my past :-P.
Could you make it so, that the event switches back to "none" when you change it?
And one last one: When you select an BGO (or NPC), put it into a layer and then change it to an NPC (or from an NPC to a BGO), it still is in that layer. This dosn't applies for blocks, though.
Could you make it so, that the layer switches back to "default", whenever you change the type of item you have selected (changing from NPC to BGO, for example)?
This would save a bit of time (but it is already very nice, that you have changed the display-type of the layers above the selected object, so it stays there without disappearing after a short time, and also that you have made it bigger)