By paintable I mean just as the road tool allows you to draw rounds, there could be a texture tool which allows you to paint textures. For example take a golf course, you would start with a base texture which would form the rough, over the top you could draw a fairway and at one end add the green. This then leads to texture brushes, you could add a feather effect to the texture which can be altered so it gradually merges with another texture e.g. from grass to mud, or cuts off straight away e.g. A zebra crossing