Thanks guys for all the info.
I'm sure time will tell how bad (or not) I need a hot water system. Given that I'm building this camper from scratch its way easier to do it now than retrofit down the road.
Here's some justification for this system that I didn't really explained earlier...
I'll be running the truck on veggie oil so the ability to heat up the engine with a small amount of diesel is a big bonus as I'll be able to switch on straight veggie much sooner. Plus, the easier winter starts won't hurt either. If it wasn't for that I'd be happy with just a FPHE (flat plate).
Using the Espar hydronic to heat the cabin while camping and the hot shower "might" be the missing link to get my wife to finally join me. (So maybe I should avoid hot water and heat all together?!!)
The big Espar story... I got a brand new Espar D10 full kit (except for the muffler) for cheaper than I could get just the basic D5 for. It might be overkilled but it was hard to pass! Hopefully the 4 temperature settings will let me dial it in as needed.
I've searched and found a lot of good info today on hot water system by searching "hot plate" as suggested. It got me to keep in mind winterization and a few other issues.
Thanks again, keep it coming!