Woohoo! I now have my very own route builder. It's simple, and only exports as GPX, with zero support for TCX files, PoI's, etc. It uses pretty much the same routing as what's in CycleStreets, and I have an option between which I want to use. I can switch between various maps, too.
I cannot use that to build #GoCycle multi-day route guides, as those have to be TCX files, to allow me to embed the oodles of extra info those route guides have. However, I *can* use it for the traffic-free route guides on #WillCycle. The route builder's not public - it's just for my own usage.