What are the best practices for either dual mono & stereo airing programs/files?

In our situation, we transmit either stereo or dual mono programs depending on our clients’ pushed files. What are the best practices to ensure my playout output will not cost audio fluctuation if the contents that I will be playing are combination of programs either dual mono or stereo audio? As broadcasters we want to solve this problem not by looking at the receivers end(cable network, household tv, international tv network that will air our files), but to enhance or modify through our transmitter.

Example scenario: We air programs that are combination of either stereo or dual mono but the receiver(old tv using antennas) usually relay mono. So if a stereo audio program is aired, the scenario will be the old tv will play mono. Because of this, there will be loss and sometimes fluctuating(changing) of sound levels will be observed.
As broadcasters we want to solve this issue not by looking at the receivers end but by what we can set or modify in our transmission side.

Re: What are the best practices for either dual mono & stereo airing programs/files?

If acoustics or multiple sound sources cause out-of-phase sounds on the channels when a stereo program is recorded then of course that part of the sound will be cancelled when played in mono.
Haven't you heard a choir or group of musical instruments with fluctuating sounds? It is normal because the sounds do not all have the same frequency and phase, frequently they add then they cancel.

It might help if you switch your stereo compressor so that it acts in mono so that both stereo channels are compressed or expanded at the same time. But then stereo might sound weird.