If resolving naming-conflicts in a fair way should matter more than resolving them in an easy but unfair way,one could consider several criteria like playtime,level,ingame-achievements and date of character-creation to feed a scoring-system where the higher score takes precedence when both characters with conflicting names are active.

It would be easier to accept the loss of a name you really care about,if you lost it to an other player who really played the character and put an amount of effort into its development like you yourself did or even more so.