We brought a 25B new 5 years ago. The reason we picked this floor plan was basically the reasons you gave. We have not had any problems with it. Have made several 2 to 3 weeks trips around the country. Did do the heavier sway bars and Sumo spring upgrade to improve handling. It is on the 350 chassis with a V8. We tow a Wrangler and just made a trip to Colorado. It did fine on the passes, just let it gear down and the engine rev.
We have a Yeti type cooler that we set at the foot of the bed that we use as a step to make getting in and out of the bed easy.
The only thing that I would do different would get the 450 chassis. With the Minnie loaded to travel with the wife and I, weight is around 12k, leaving only about 500 lbs to GVWR. The extra 2000 lb from the 450 would allow you to carry more passengers and cargo.