Even if the jets developed enough power to lift a useful load,and as pogno said,could carry enough fuel!!If the wing section was unchanged one would soon get into the situation where the stalling speed was about the same as the critical mach number.
From memory the U2 suffered that problem and I seem to remember reading that if you tried to turn too tight at very high alttude you could have the situation where the inside wing might be in stall buffet and the outside wing might be in mach buffet!! Hard work without an autopilot on the early ones.
Also from memory on the early U2 at very high altitude the difference between stall and Mcrit was in the region of 7 knots!!

As much as that? I heard it was more like 5mph. With regard to the problem of the wings in a tight turn, they should not have expected them to behave any other way when they stuck a jet engine in what was little more than an all metal glider. You could have produced the same problem by putting an Allison C-250 in a Blanik 😀 (anyone remember them?)