Anything's possible given enough money or resources. Sounds like a fun challenge.
A truck camper is pretty small, which means a small volume to heat, but also means there's not much cargo room for resources. Can you carry two large propane bottles, someplace they can be wrapped with heating blankets?
You mention electric being available, are you talking 10 amps for a block warmer or 50 amps for a big RV (or whatever the European equivalent is?) Do you need to drive the truck to work, or just live in it? That is, will you be unplugged for most of the day?
Are no separate hygiene facilities available? Not having to use the on-board water system makes it less of a problem keeping the interior warm all the time.
