I had this same thought. So if you are building a traditional style MMO where you are worried about cheating, then this really isn’t possible. However, if you are building a smaller Persistent World Multiplayer game where people just play with their friends then this is totally possible. In fact it is easy!
Because of how I built my World Server component, all you would have to do is bundle the World Server program (a small Windows EXE) with your game and then each player would be able to run dedicated server maps and you wouldn’t have to pay for any server hardware except the Management Server component which will be very cheap to run as it does not run UE4 and only runs my very light server software (.NET MVC service + SQL Database). When a player starts up the World Server app which would startup with your game, it registers them as an active World Server with the management system. When this happens you can set what is the maximum number of maps they can run. Then the management server will dynamically assign maps to their hardware as needed.
Added note: As far as performance, when I play my game with friends I run 3 or 4 dedicated map servers on my PC while I play the game with no noticeable FPS decrease. I have an AMD 1090T CPU from 2009 and 16 MB of RAM.