Not to suggest that this is a best practice in general, but..... In marine applications batteries are paralleled all the time. One common reason to be sure that you can still start your motors after running the aux loads all day. The simplest switches just switches between batteries or parallels them. Which connects the heavily discharged battery with fresh one. If you think your average small boat owner buys their batteries the same time in match pairs, don't know many fishermen.
In parade situations, we just live with the time it takes to cycle the Crio while changing batteries. I don't think you are doing anymore damage to the batteries doing it your way than a typical round at competition. You are losing a little energy the gets dumps into the discharged battery while switching them