been thinking about this
could you not harness the CO2 that is being produced at low levels by the yeast , capture it , and then use it to push the beer out and keep you ale nicely carbonated at a low level of Co2
If you were to Jury rig a car inner tube to a UST bike valve installed in the lid area, then as the beer secondary feremnts it blows up te inner tube like a balloon but at afew more psi. Then , as you remove beer from the bottom some of the CO2 goes back into the barrel to fill the headspace and equalise the pressure
Beer would keep for maybe 6 -8 weeks like this.
Might be a tiny amount of smell pick up , but probably not noticable .
Bike tubes too bulky , and low volume , maybe a wheel barrow tube might be better .
The Co2 is there , I imagine a car tube will hold 3 – 5 psi without failing , anad if it does look like its about to pop just deflate it .
Would need valve cores removing to allow gas flow both ways . Balloon blow up at too low pressure and im pretty sure the CO2 would vent through them as they appear permeable to gas .