I am not sure if the sheer speed of the updraft would be too much of a problem. As long as you are in a consistent airmass. I have flown gliders in mountain wave, as long as I allow the updraft to carry me and I hold same 'speed' and attitude all is well....
But, along with the updraft, close by is an equally strong downdraft.. and, inbetween, extremely rough rotor and disturbance that can break your craft by exceeding G forces.
Add to that, HAL trying to maintain the programmed flight plan and getting overwhelmed by the external changes....
In a CuNimbus scenario you will have extreme airflows up and down. Trying to poke a hole in that cloud at speed will give you extremes of G and not to mention super cooled air, icing etc for your wings, pitot tubes etc.
Best to thread your way around them as most do.
They asked for permission but left it too late and drove into a super cell perhaps
