Elliot, I respect the fact that you have put a lot of effort into mono playback of mono LPs, but I have to question the following statement, with reference to some shortcomings you listed above of using only a mono mode switch to listen to mono LPs:
"It DOES NOT reduce any surface noise, warps, debris, any vertical movements picked up by a stereo cartridge, it in fact doubles that, as any L or R are combined, then doubled."
I was taught by reading that the L and R channel noise(s) generated by dirt or damage in the groove walls are (predominantly) out of phase with each other and will thus be cancelled when the two channels are combined, as when one uses the mono mode for playback. This concept is consistent with my repeated experience that HF background noise is reduced when I listen in mono mode (without also using a mono cartridge). Also, I don't quite get what you mean by "doubled". If the noise is cancelled because out of phase, then nothing is left to double.
The whole discussion is complicated by what definitions we use for "mono LP" and "mono cartridge". So we could be talking past each other. As you know, most mono cartridges for sale today are actually stereo cartridges in which the two channels have been bridged internally, in order to generate a mono signal. That is really no different, except in one way, from using a mono mode switch on a phono stage or linestage. The one difference is that in the former case, the mono signal is generated BEFORE RIAA correction and amplification takes place in the phono stage. Whereas in the latter case, the combining of the signals happens after those two processes have occurred. (Using a Y-adapter between the cartridge and phono inputs is really a bad idea in my opinion, because in that case each side of the cartridge is seeing the impedance of the other side in parallel with the input impedance of the phono stage.) So I can believe that a mono cartridge, especially a true mono cartridge (one that is built so as not to respond to vertical motion of the cantilever) might have advantages vs using a mono mode switch.