Enable sending a finished solo game as a challenge

Sometimes I play a solo game, get some unique/interesting locations and want to send it to someone else so they can play it. But of course since I started it as a solo game I can't. Currently the only way around this is to start every game as a challenge game, copy the challenge link and only send it if you decide you want to. Obviously, this is cumbersome. It would be super handy if you could send finished solo games as challenges.