Just run multiple dedicated servers on single machine and bind them to different ports or IPs in your disposal, thats common practice in game server hosting business. I mean you can’t find much games that do what you describe primery because you can run multiple processes in one machine. Not to mention running other (software) servers on sperate process improves multi-threading as non-used cores can handle other server and way you describe it (which is is indeed possible but only via C++ and creating new world instances, i’m not sure how it would work with replication) won’t do much diffrence, UE4 (and machine as result) still would need to handle each world sepretly.
I think what you aiming for is similar set up to Rocket League (which is game made on UE3), which has lot of dedicated server running running all the time. and they have match making servers that monitors those servers and connect clients to selected free. I know this because you can see server name when you join the game, now sure why they placed it in HUD ;p
The biggest challenge is match making server (not sure if Steam for example can handle that for you) but it easier challenge then running multiple world instances and you could set it up over HTTP and ofcorse cost, as more players you gonna have, one machine might not be enough, Rocket League had that issue, but primarly was caused by prefermence issue of there match making system, when game appeared on PS Plus people jammed the server.
Alternatively and i think you should consider that, is let users host the games, PC gamers love that aspecially if your game is compatitive, clan severs are have thing and game server hosters will be happy to provide them hosting without you paying anything, but on consoles i’m not sure if Sony and MS allows this setup