"I have Battery SOC info off my MT-50 display".
Nah - not really. From the MT-50 manual :-
"The Battery SOC% is an estimation based on the charging voltage". (For "estimation" read "rough guess"). What you need is a proper shunt-based Battery Monitor that logs all current flowing into and out of your House battery. Prices start at way less than you paid for your MT-50 display unit.
"I’m going to grab another meter and have a play around setting the chargers up on a seperate circuit with it’s own shunt and meter, that should give me all the info I want."
All meters involved would need to be capable of measuring AmpHours, not just current. But don't you want this information in an easily understood, readily available form? Think about what you would have to do to get any sort of SOC% estimation. Starting from a known battery SOC Ah, you would have to add "charge" Ah from all sources, then subtract all "discharge" Ah, then divide by the battery AH capacity, with the result expressed as a percentage.
"Or I could just go old school and throw a 200 amp meter inline".
That still won't tell you what you most need to know - the battery SOC%.
"Could I wire another of these in reverse on the existing shunt to give me the amps in?"
Yes, you could, but knowing the amps in at any given time will not give the AmpHour figure that you are lacking. You would be throwing good money after bad, ending up with bits and pieces of gear cobbled together and still not having a readout of your battery SOC%.
"My end goal is to have a seamless power management (translation = my wife and family can use the motor-home in my absence without needing a hour long dissertation in the intricacies of power consumption and battery maintenance)"
That makes good sense - so why don't you want to fit a proper Battery Monitor that would give a simple "Battery %" figure that anyone could understand?