You would not need to wipe friends list or guilds... global rankings could be updated quite easily.
You would given players play on multiple worlds. If I play (for example) on both Brisgard and Cirgard. If hypothetically you want to merge both those worlds. You’re going to have conflicting data.
What happens to my actual city on both those worlds? Wouldn’t have space to put down everything from both cities even if I wanted to. Wouldn’t be fair to expect to retain my ranking, inventory and city buildings either. It wouldn’t be fair to those who only had one city to suddenly have to compete with those that duplicated results on a second city and then had it combined. I wouldn’t want to lose my progress on one of those cities to retain the other city either.
You also would have to lose all your Great Building progress for one of those cities because you can only have one of each GB and you can’t just move the contributions (the amounts are different for each level)
What if I’m in two guilds? Which guild do I stay in? What if I’m founder on both? What happens to the guilds? Can’t merge guild treasuries without making it unfair to those that don’t have a second guild to merge with. Can’t retain GvG progress either. Can’t go above the 80 member limit if merging guilds
Friends, you have max 140. Even if I only have 80 then you can’t merge the lists because that’s 160-280 friends. You’d be over the limit
What "bugs" could possibly occur? Worlds/Servers are merged on other games just fine with zero problems.
This isn’t other games. I have my reasons for believing it would be far more likely to go wrong then it is to successfully merge. I can’t properly go into details on the why I believe that due to the nature of the reasons, but I have my reasons