Bernie would be very dangerous in such a race...but the goal should be to end the two party oligarchy, so even a Bernie win would be some progress. Governing chaos would ensue, but that’s going to happen anyway over the next four years regardless of who wins. You will likely get some different form of gridlock and creeping socialism, which is pretty much what you’d get from the two party system. Over time, however, there is an opportunity for real change, but only if the two party oligarchy is destroyed.
If Bernie wins and the house and senate stay under GOPe control, oh screw it, they will bend and give him everything he wants, they did with Obama