I understand that the problem (feature?) of getting highly inaccurate readings from a gasoline capacitance fuel probe that is submerged into a gas tank with a puddle of water in it is not unique to home-designed systems.  This is characteristic of all of them due to the capacitance difference between gas and water.

I wouldn't bother incorporating electronic features to remove that characteristic.  Remove the water instead with your fuel drain.

I might actually consider this a "feature", since you might be able to detect water in the tank that way.  However, I suspect you'd have rough-running (or non-running) engine problems long before there's a big enough puddle to engage the probe.

- Rob Wolf