Yes, I think it would have to be compulsary. I don't think there's necessarily any need to do away with pit stops, but it opens up the option of a driver doing 2 or 3 stops on a really soft tyre or 1-2 stops on a harder one. But can we PLEASE do away with this idea of having to use both compounds?
The overriding principle is that what ever they come up with has to offer as much mechanical grip as the teams can get from aero downforce, or they'll carry on trying to come up with better aero packages.