I think the argument now is that the new aero designs cause the displaced water to reduce visibility much more than before. To be honest, I don't know enough about aerodynamics to know if that's true though.

I think you're right about the minimum "driveable" conditions being higher than in the past. I don't know what the solution should be, but I really hope they figure out a way to make wet racing possible too.

Let's be honest here, the only thing needed to prevent a Bianchi situation is keeping the machinery off track until they've all caught the safety car. The cars can hydroplane into walls all day long and the drivers will be fine.