This is late, but I just had a lightbulb moment!!!
next time I do this I'm going to have a hose coming out of my airlock (like a skinny blowoff tube) thats connected to some kind of variable volume bag. The bag will be filled with CO2, and allow co2 exchange in and out of the fermenter. right now for a bag i'm thinking that a wine bladder might work well. also those collapsable cube containers that some of the online HB store sells might work.