... the solution some other types have, whereby the two pumps take their feed from different levels within the sump.
I agree of course. The problem with a gauge is that most crews don't fly along looking at the gauge all the time, therefore a departure from normal is only noticed once it brings on a caution light. This is the situation we have in the Super Puma family - a leak reducing the level in the sump will eventually uncover the inlet to the main pump, bring on a light and automaticall bypass the oil cooler. So you get the low level warning and bypass selection intrinsically, from the way the hardware is designed, with no moving parts or clever circuits to go wrong etc. It is a far better design strategy than having a separate electronic level sensor in the difficult environment, separate electrics to move a solenoid valve that only ever gets used in an emergency etc. That is why I am glad I fly EC!
HC