Lot of questions at once. Can't directly reply to some but I can for others.
The Accord will work well as a toad. Honda does not recommend to do so for the model year you listed but the transmission will handle it. I have the same model year but a two door that is next in line if the primary, 2005 CRV, dies.
Both towing options each have advantages and disadvantages. Dolly will greatly expand the line of vehicles that can be towed but it might be a bit more work at a camp site. Four down is simplest but you vehicle selection is a bit narrower.
Critical items, washer/dry (individual units) would be high on my list. Residential fridge, heat pumps, dual pane windows will make life a bit easier. Top of the list though is a floor plan that fits your life style. All the options in the world won't make up for a floor plan that is a problem for you.
Tag axle does have benefits but generally you don't see them often on a 40' or shorter coach. Foretravel is the first builder that comes to mind for a smaller wheel base rig with a tag. The additional axle will need maintenance along with two more tires and higher tolls if you happen to venture out on a toll road. If you're not afraid of older rigs this
Foretravel would be a really good choice for full timing and fit a couple of your "in search of" items. The ISM based power train will get you to the top of Pikes Peak if they allowed rigs up there.
I wouldn't worry too much about coach builders that have stopped production. If you dig into everything in a coach the list of what the build supplies really isn't that big. All the appliances are from someone else, majority of the chassis are out sourced. Might be a factor if you damage the front or rear caps and need a replacement but with any builder coupled with an older model finding new external replacement parts could be a challenge. The one item that would concern me is an in house chassis with an out of business builder. Just not sure who that might be off the top of my head.
Good luck with your search.