I thinks its very complex to do that.
This whole Game musst be modified (Server, Client, Binary, DB) to safe all Data which needed to run this Game on your Computer. The Serverfiles works on Linux (FreeBSD)
and our Client on Windows. Now its need a Way to run all Components from Linux on Windows (MySQL and the Core and some Maps).
I think the only Way to do that, can made possible by installing a localhost Service, which starts during Playing this Game.
Another you find People, where write your a complete 1:1 Core for Metin2 without any Internet Services.
Its a nice Idea to make a own offline Game with a Story..
But to implement it, will need very deep Changes in the whole Data Structure.