I was driving home today, and got a reminder that there are ALREADY commercially-available diesel-electric plug-in hybrid trucks that I see nearly every day!
The local school bus company owns 14 hybrid busses. Here's one I took a photo of at a traffic light.
The best part is that they solar-charge them! The car port that they park under has a giant grid-tie PV array that nets out to how much power the busses use through the year. I believe the bus is
THIS ONE, in case you are interested.
I also dug through my box of misc EV components and found that DC/DC converter. It's rated at 15 amps at 12V, and has an output voltage adjustment, so I should be able to turn it up into "12V battery charging range".
It's a brick that's about 8 x 2.5 x 4 inches and will run on 110-330VDC
I think 180 watts should be enough for a truck DC/DC converter. Regular headlamps are usually 55 watts each. Taillights and radio can't take much power. I'm not sure how many watts the heater blower runs, but if I was in EV mode anyways (and thus using the DC/DC instead of the alternator) I'd probably just be using a seat heater.
There's always the possibility of converting to HID or LED headlights as well, which should also lower the 12V power load.
I guess technically, this is just a power supply, but it can run on either AC or DC.