We had a 19T4 for 7 yrs, and they do have a lot of storage for their size!! Loved the sideways bed and front drawers.
Our Jayco does not have any more interior storage, probably a bit less, but does have as much or more accessible outside storage. Larger counter top, more food prep area. It did suffer from less freshwater until I added another 30 gals under the sofa. Holding tanks are somewhat smaller, but haven't been a problem.
We also camp in cool weather, and will suffer the sweaty window syndrome, but we mostly use the trailer for sleeping and other functions and spend almost all of our time and cooking outside, which reduces the problem for us. And most of our camping is in pretty dry areas of the west.
Like you, I would like to find (someday!!) a trailer that could be ordered to my specs and ideas. But, with the prices of today's units (built only one way) a custom one probably is out of my reach.
