The current iteration of the game will be getting taken down and replaced with the updated version on official servers, no? During this process, just have another server with the same old patch up. The patch they are releasing already exists, they are just implementing it. There is no “current patch being “maitnenced” on”. It gets removed and replaced.
Would it be crowded? Sure! There would be the issue of figuring out exactly how popular something like this would be and dialing in the allocation of necessary resources in order to possibly create multiple sandbox servers.