In my head, I imagine the perfect (maybe) scenery creation scheme, where from an overhead view, a designer (maybe with a map overlay) could use a graphics tablet to simply draw roads and rivers, draw tree boundary lines and have them autofill: place houses with a tap of the pen.......
OSM has already these types of local informations, and I guess we should see it in Outerra at one point, since Titan will probably require a dataset importer. Majority of the editing will probably be handled as dataset preparation in the future, then local editing for stuff requiring high quality details (airports, local POI) depending what you want to do with it. It will probably better to do the type of work you describe inside of OSM, so this will not be exclusive to Outerra but to the other users as well
And I can assure you that with a bit of experience, the road tool is really straightforward to use. The area you see in the previous screenshot is a one hour work
The only real lacking feature for the moment is the capability to add non linear shapes (areas) in the engine. When it will be possible, and with a bit more specific profiles, even the capability to add custom ones, you can do almost everything.