FOSS gamedev and creative worlds

Is it possible to build gateways that can link 'worlds' on a server through a gateway of sorts?

that would require a mod that works independent of a game, to log out the player from the 1st game and log in to the 2nd game. since mods are loaded in-game, they can't function outside the game, so it's not possible.
transferring player inventories and status between games is also currently not possible.

the only way to simulate travelling between worlds is a layered world mapgen.
then the player can be teleported to another layer "world" on the same map.
i guess the different layers can be separated from each other by adding a layer of "ignore" nodes between them.

you can use teleporters to teleport people to different places within one world, e.g. the surface area and nether realm or whatever you want to add, but you can't teleport them into another world.

could you maybe use external programs?

Perhaps I am talking about something that a client would log into that would maintain a character 'world to world'. Keeping atrributes and stats and items as they move through the network of worlds. Naturally, the worlds would have to have common libraries for items moving around, but I don't know, I just think it might be really awesome. I can't do it in one world because I am having memory issues and I crash about anytime I go further than a few kilometers from my starting point. I can envision a complicated outside scheme, if I figure out a solution I'll certainly share!

good luck! (in a good way)