I would suggest giving a framed, or frameless, pontoon boat a look. Granted you will still be in waders (although in warm weather I've just worn shorts when I forgot my waders!) but the plus side is that you are sitting much higher out of the water so only your shins are in the water. I've never been cold. Because you aren't half-immersed in water, you can get by with a pair of breathable waders that are much easier to get in and out of.
I've fished out of an 8 foot framed pontoon boat (Outcast and Bucks Bag) for the past 15 or so years. I avoid all things boat-related (aluminum, motors, gas, batteries...) and prefer a person-powered inflatable, perhaps for the same reasons that you like float tubes.
I only fish upcountry stillwaters for 5 days a year in my boat but it also gets used in local sloughs and lakes, even tidal rivers. I keep the boat assembled and inflated and hung from the ceiling of my garage. I can drop it down, load it into the back of my truck and have it strapped down in minutes.
For my purposes, it works for me.