I did think that could be a long-term aim.
I don’t understand - you know the current, there’s almost no loss to capacitance, so it’s the same current at both ends of the cable (certainly to better than the accuracy of the c.t’s). The losses are almost all I²R and you can calculate that.
That - depending on how much spare wire you have - should certainly be possible with the 10 circuits handled by the transfer switches, one c.t. per leg (automatically accounts for 120 V & 240 V circuits if you use 120 V as the voltage reference.
Yes - or at a circuit fed by the inverters. When the mains disappears, you’ve got no voltage reference for those loads.