A couple of notes:
1) The furnaces that have a fan generally seem to require electricity to power the fan. In other words, you cannot run them without the fan (at least the ones I know of). Now, that electricity can come from a battery
, but they do take a fair amount of juice over a night.
Some of the older campers have "gravity" propane furnaces, that did not have a fan, and require no power. These are not made anymore for some reason.
2) I hear you on the work table. I sometimes like to do projects and like to have a workbench/work table. I change my camper around several different ways depending on what I have going on. I have a 13 foot Boler
A) Somtimes I made a full width table about the size of the couch in the front (over the couch space). I can then put a chair or stool in the middle (so I'm facing the window) and sit there if I want to. This of course is for when you are solo or sharing the double bed.
B ) I've slept on the front couch (back/bunk removed for more space), and made a little U-shaped office type area where the rear dinette is. Office type chair in middle of U.
C ) Currently, I have the full time "double" bed in the back, and one thing I find indispensable is that I have a "table" across the foot of the bed (it runs parallel to the kitchen, as if it were an extension of it). This gives me an ~18" x ~42" table/desk, and also I can put my sleeping bag under it during the day. It's just a lightweight piece of 1/4" ply with cleats under it which spans between the table support in back and the sink counter. Easy peasy.
D) In the front, I have the couch (with matching "counter" over the kitchen end), and sometimes I put the bunk top back in and raise it to give me more "surface" space.
E) I may make a dinette in front.
I guess you can tell I like a bit of flexibility - it just depends on what I'm doing at the time, and if I have a friend along or whatever. Maybe I'm anti-social (no, no need to answer
), but I can't imagine sleeping with two or three friends in the camper (i.e. needing the bunk for that). More than one and a tent would be set up!
One other note is to consider how often you really would have people along. Not to say you wouldn't, but in boating I can't tell you how many people lug along an extra 10' of boat for those friends that "might come along" but never actually do (or very rarely).