The shunt must be wired into the negative side of the battery
bank with NO other wires (loads or sources) connected to the battery
connection side of the shunt.
There are no tricks to getting around this fact.
Like Jentine says, what is your problem with wiring
it on the correct side of the battery? Any argument against placing the shunt on the negative side applies to the positive side as well.
If you have significant physical separation of the batteries comprising a "bank" then both the positive as well as negative wires must be planned to have the same parasitic resistance for both positive as well as negative wiring
including a wire size appropriate to cover the potential losses at high currents.