Im sure i can think of one, but looking around my g20 its gonna be tight. If you have ventilation, a butane stove like the one listed will boil it no problem, and it is small enough to fit on the desk top. I cook in my van all the time, a vent helps but window and a fan will work. As for the loo, you may have to fashion a small bathroom area for privacy. or curtain off the front cab, place loo in front between seats, curtain side windows and sunshade front window. cab acts like a seperate private room. As for standing...i use a rolling office chair, seems simple but i just immediately sit in it upon entry, i transfer to bed or rotate/move around as i need to. its probably the single best think i added. You could consider a swivel passenger seat modification, one of you sits there (slide curtain over), other sits in chair or bed etc. Lost items just happen but everythingf should have its place and ahould be put there...no helping it in tiny homes. Drawer storage helps. also there aree these bins at lowes ill post, i screwed them to the cieling (be sure to put wood up or something, don't penetrate roof), and they have a semi open front...like cabinets without doors. They work on the floor too.
Its doable i think but its about what makes you comfy. there are couples so in sync they live in astro van with dog faiely happily
if you cant screw to room safely, maybe a very strong adhesive. you dont have much verticle space, but use
http://www.lowes.com/pd_149439-8424...rrentURL=?Ntt=plastic+stacable+bin&facetInfo=
Also that cube storage or something similar would help a lot with getting organized. Even the 4 cube. i got the idea from a youtuber who used a much bigger toy storage unit from ikea. They have cloth boxes that slide in like big deep drawers.
here is my old g10 (same thing, regular wheelbase), using some of these elements in my build
Also consider moving stuff you use outside the van or less often (camping gear, recreation stuff, tools) to a rooftop cargo box. that will free up space.