All of what you have posted makes perfect sense ..... To you. The title of this thread asks should I replace or add to the current sofa bed mattress. Our MH gets used in a few different scenarios. We camp alone. We camp with family and we attend races. All of these situations require different sleeping needs. When alone the sofa bed is a sofa. With family or friends we can go with the couch, the bed and or the table. When doing NASCAR we need beds. Our company don't need or want to sleep on the floor. We are not full timers so the extra storage space isn't a necessity. Great project but does nothing to solve my question of what others have done to improve the sleeping comfort.
If you have friends who make you laugh, spend lots of time with them.
2008 Winnebago Sightseer 30B