Yeah, I think you have the basics already covered here. I personally don’t need any frills. It was the only idea I could think to add, but if your map data format doesn’t already use some kind of bitmap layer, it would obviously be significant extra work to add freehand painting.
I think you already have everything we need here. I am currently ‘faking’ my way through Pool of Radiance, trying to just remember more or less where things are, but I could really use this tool. I keep wasting time wandering around.