I have built with pentode front ends, but not exactly this way. I built a shunt regulator, and had g2 referenced to ground instead of the cathodes. The cascode experiments showed the importance of referencing the upper grid( the faux screen/g2 ) to the cathode node. I have contemplated a resistance loaded EL34 for this job in one of the high voltage amps.

The EL34 is a bit down the road at this point. The more complex cascode seems to be the better option at this point.
regards,
Douglas