Is it possible to create a desktop in the Activity Manager that instead of an image for a background u can use an application such as Midnight Commander? (or the appropriate KDE equivalent, in this case Konqueror) something similar to the Search + Launch layout available in Desktop Settings - Plasma Desktop Shell dialogue box (right click context menu>>>default desktop settings).

At present in the Search + Launch desktop there is a button linking to Konqueror, what I'm thinking is the idea that this app (Konqueror or MC) would be running all the time filling the whole background screen, as if it was an image, and other apps could run on top if needed.

Hard to understand I guess, just a thought about how to use KDE Plasma.