The thought is entertaining, but there are several serious problems.

1) The large signal and drive power necessary would require an output tube, so unless one simply wants more power, one is simply reproducing an output circuit twice.

2) The cathode is the filament. This creates complex problems. If the tubes were indirectly heated, the problems would be considerably lessened.

In either case, the fidelity would be lessened to a considerable extent.

Hope this helps.
Steve