Dont see any reason a parallel panel wouldnt work. shouldnt have to be same manufacturer as long as its compatible with whatever device(s) are in the tank. I agree that would be a nice factory option! Though mine i can usually hear pretty well through the vent as long as theirs not too much noise out, itll gurgle for a few minutes before it starts spitting water out.
As for the pump, maybe its just me, i cant see any reason i would want/need a pump switch down there? If anything maybe set it up on a timer relay so it cant be left on unintentionally. it would really suck to have some kind of water issue inside and the switch inside is overridden by the outside switch, so your running all over the place trying to shut it off while everyone is screaming