There is a soulution to it.
Frogster can offer ppl to keep their name or take X amount of diamonds lets say 2k. If the character was created before whatever date and has been active then this would apply. If both choose to keep their name then frogster can force them both to change because of a problem with their name. If both players are willing to change their name, then problem solved. Name will be come locked for X amount of time (lets say 90 days), and if the players so choose, they can get a name change when the lock is up. So which ever player is able to buy the name back can have their old name on the server preventing the conflict if both chooses the dias.
As for guild names, it should depend on active guilds. I know alot of ppl will be mad because they have banks with names and such, because I have a guild for a bank, but if there is a guild on Grimdal with that name then its not right that my bank guild prevents them from having their name.
So if there are 2 active guilds with he same name, I think that the same rules apply, and everyone gets a free house re-name or name if you havent done it and password