Even when I do DCFC my PHEV, it only takes 20 minutes total. It's not like I take up the port all day. If a BEV has to wait an extra 15-20 minutes, too bad for its owners. They knew the limitations of having a BEV when they bought it. If they didn't want to have to depend on having a charger available, they should have gotten one with a longer range or they should have gotten a PHEV.
In any case, the solution, if all level 3 chargers or level 2 EVSEs are occupied, is to build more of them, not try to control who uses them and who doesn't.