Jeff, this is a great thread. You have hit on everyone's dillemma... how to have "everything" you want with nothing you don't. Having had about a bazillion trailers over the past five years, my official "counsel" is that it just ain't gonna happen. Every trailer has trade-offs, and you are one of the few folks who have enough tow vehicle to really take "everything" with you... just not in a 13' trailer.
I'd suggest you try the Scamp
stock a few times, and the decide what you really "need" vs. what you "want" in a travel trailer. THEN
, you can make informed decisions about what you and your spouse "need" to do. You are almost always better off buying a unit with a bath than having to engineer one from scratch in a built trailer. There are more important issues though. If you're over 5'7" tall, and more than 150 lbs, regardless of the size of your spouse, you're going to find the bed in the Scamp
13... limiting. If you don't rest well, your outings get old... fast.
I'd also have to say that you won't need three tanks. Most folks who are out for a week have access to propane
somewhere for refilling as necessary. I'd seriously doubt you'll run through two 20lb tanks of propane
in a week cooking. I used to have two 30lb tanks on my Airstream Safari and they'd last two weeks using the furnace
pretty much full time. I have yet to auto-switch off the first tank in my Bigfoot
and it'll be going on it's third camping season.
I've had two Scamp
13s, a Scamp 16' Custom Deluxe side dinette/front bath, a Scamp 19' CD fifth wheel, a Uhaul
CT13, a Trillium
4500, a Burro
17' wide body, a Love Bug
18' wide body, a Bigfoot
15B17CB, and now a Bigfoot
25B25RQ. (This doesn't include the half-dozen Airstreams I've had in the past ten years...). Why I've had all these is another story entirely, but what I've learned is that what I need to enjoy trips are a large bed (80" queen minimum) is a must, and a shower that's big enough to actually use in a trailer light
enough to tow with a half-ton truck or smaller tow vehicle.
Having done significant repairs to most of these as well, I've also learned to look for simplicity of engineering in the systems (water, sewer, electrical
etc.) for ease of long-term service.