so if like one spot is taken on all three servers, when they merge, and you approach the spot, you can examine a list, and it informs you of the 3 different guilds, and you select which guild haven to enter. It shouldn't be too hard to code, I'm trying to remember the haven world set up, but I believe they are on a separate server compared to the actual game worlds, so the possibility should be there to connect them this way.
But this is only speculation from a man who is using 2year old information and personal experience to tried to understand Ankama code and possibilities. So don't get too set on the idea.
And guild names might have to be based on guild duration. Seniority rule, oldest guild keeps its name. I mean, I'm already hearing about a bunch of people finding their character names already taken on Remington by others. Some could be coincidence, but others are definitely purposeful name theft, judging from the scale of unavailable names.