What are the modules that you currently have installed? It's my understanding that the +/- leads out of the modules j-boxes are not PV wire, is that correct? The reason I ask, as I'm sure you are already aware, is that for transformeless inverter this type of wire is required coming out of the modules. If their wiring is not PV wire, then I am stuck at the moment in trying to match you with an inverter that has dual MPPT channels and contains an isolation transformer.
I am happy to do some more digging for you, but having a little more information about those modules, the number in each string and the orientation of each array will help me to better understand your system.