... we can't replace it with anything that even vaguely meets our requirements: doesn't get WORSE mileage, has a pop top that we can stand up in, is comfy for sleeping.
@jeninco - we bought a lightly-used Ford E350 cargo van for our jetski towing and camping weekends (which we've been doing since 2003). We started with an older van, which didn't have an airbag for me. After 5 years of that, DH started agitating for a "van improvement project" to add a raised top so he could stand up in it.
I told him we weren't spending that kind of money on a nearly-10-year old van if I didn't get an airbag, so we sold that van (getting a very nice sale price, because we care for our stuff!), and then turned around and got a 2 year old E350 that had better towing capacity, and dual airbags.
We then did some very judicious improvements: a Fiberine top, insulation, window shades, and a ledge over the front seats for storage. The Fiberine top got two large sliding windows installed. We raided the junk yard for pop-out windows for the rear windows (no longer standard, due to concerns of CO2 poisoning when driving, and we only ever open them while camping).
We bought a camping fridge that is good for a 3-4 day camp when you add ice, and a backup camera that gives you a view while backing up to the jetski trailer in the rearview mirror.
All in, including the van, the labor for the Fiberine top and interior upgrades, was about $25k. And several years later, when we moved to a house on the water, that van has the towing capacity for a boat and trailer.
We found a lot of help on the DIY forum for Sportsmobiles; folks pay $150k for crazy van-built upgrades, but the DIY route can be very cost effective, with a little help from a conversion van or body shop if you want a tall top.
https://www.sportsmobileforum.com/forums/