My dealer tried to tell me the '22s got them because they needed it for cranking the engine over in alpine regions. It's bull, the single battery is sufficient and remarkably close in capacity to the single battery found in the identically-engined D40. I didn't call the salesman on it because it wasn't a big issue.
There might be some reasoning that D22s are more for tradies and tradies need more mobile power than us salon owners, because the intention behind the D40 is to make it a tourer rather than a worker (fine by me, that's what I bought mine for!).
In any case, you can either pop it out and have the spare room to put a larger airbox in, or you can drop in an isolator and run some (30A thermally fused, 60A paired double insulated) cable to the tub and run your gear down there.