Even if you are close to the limits, the switch to Alternate law is really not as big an issue as you may have been led to believe. The controls handle in exactly the same way as in Normal law. Assuming you have been placed close to those limits by an unexpected surprise, the fact that you are close to the limits is more than enough to prime any competent crew to take corrective action. People don't simply wait for the aircraft to sort itself out, they take action themselves. The FBW protections are only there in case they don't take action. In Alternate law the aircraft will permit you to take almost any action you wish to correct the situation, and the transition between Normal and Alternate will be essentially seamless. There is no need to have a 'big brother' system to tell you that there would be a risk in Normal law dropping out because there is no risk in Normal law dropping out.
With reference to the Air France accident I don't really see how control law issues would be a factor. If the aircraft is in severe turbulence then overspeed/underspeed protections are an irrelevance as the aircraft will be in and out of both continuously. Any implication that the aircraft is harder to control in Alternate law is turbulence is questionable as it handles the same as in Normal law. If it's an unreliable airspeed situation then you fly it like any other aircraft by setting pitch and power and watching it like a hawk. The unreliable airspeed drill is really no more difficult in an A320 than it is in a B744.