It's surprising how difficult it is to find new technology sometimes even when you are looking.
I have searched for a 'square' feed bottle to provide higher capacity in the same space and failed. I have searched for a battery type that is more convenient to use and failed also. There is only one maker of a 5v battery that would let us avoid stacking and from the
reviews it does not last very long for the size.
From everything I read the real danger of batteries comes from containing them inside a metal shell without adequate venting in case of battery failure. With the RSM if there was a catastrophic failure it might melt the bottle and scorch some wood but that would probably be the extent of the damage. It could not build up pressure as the huge squonk hole, inset
tank hole and adjustment hole would provide plenty of pressure release and even the door would simply pop off if there was enough pressure.
If anyone ever comes across some new tech that they think I could apply to the RSM please let me know