I think you overestimate the shear of even a very strong jet stream. Going from .79 to .85 (like I described previously) was a huge speed increase. And it took time. Had the speed continued to increase, it would have been fairly easy to pull back on the yoke an climb a bit.
Anyway, an Easyjet 737 was recorded to go 450 knots, in a botched manual reversion test. No damage to the aircraft afterwards! Though the Mach number was probably relatively low, as it happened around 10-15k feet, it is still a testimony, that these machines are stronger than what you might think.