Fuses that are not powered with the ignition and accessories turned off are not going to cause a parasitic drain, so we really only need to be concerned about the fused circuits that are permanently powered. Some of these will be heavy main fuses distributing power to sub circuits and these sub circuits will have further fuses depending on the circumstances. In modern cars some circuits have no separate fuses and have electronic "Fuses" - i.e. intelligent power distribution modules. Every manufacturer has a different name for their particular module but they all do the same thing. Most vehicles are unlikely to have more than 20 permanently powered fused circuits , (I am sure someone will find one with 21!) , so we need only be concerned with these. In addition there can be 5 or more separate fuse locations scattered all over the car - under the hood (UK eng. bonnet), in the passenger area and likely in the trunk (UK eng. boot) area too. So not an easy task to connect all these up and measure tiny voltages across fuses and hope to get accurate results. A 1 Ohm resistor plugged in to the suspect fuse sockets will do a better job & will not materially affect the circuit if the current is small. While not a "precision shunt" it is more than accurate enough to diagnose the problem quickly and cheaply without undue complication.Are there many different fuse blocks (1000s) or is the number of different fuse blocks a much smaller number? My thought being is to create a daughter board that the fuses are plugged into and the entire unit is then plugged into the vehicles original fuse block. This device could be used for the same type of vehicle or perhaps several vehicles using the same fuse block.
The device could also have onboard intelligence, to mux measurements to an offboard device. Or perform data logging as in the original post.
It’s the monolithic nature of this device that is its attraction. Removing and replacing dozens of fuses is simplified to one operation.
In the end of the day the object is to locate the circuit with the excessive parasitic drain and repair it. Multiplexing is unfortunately going to complicate matters as each input will have to be separately identified in any logfile to locate the the circuit with the drain.