This would work good to power the 12 vdc system/sterio/climate control loads, alliviating the traction packs need to power those loads through the dc/dc converter.
The roof can harvest near 300 watts or .3 kwh per hour with modern 23% efficient monocrystaline semi flexiable panels available for a mere 2$ per watt from ebay.
Several 30 watt panels each with thier own micro mppt. They can be adhered with a removable quality 3m automotive double stick tape. The power lines could be descretely run along the rain gutter roof line and fed into the 12vdc bus under the hood or under the hatch.
Then replace the lead acid 12 volt battery under the hood with a high capacity lithium battery; maby made from several leaf battery cells. Set the mppt's to fill the lithium battery to up to 15 vdc then the traction pack dc/dc will remain off until the pack drops below 12 vdc.