How about a option that allows you to view someone's old usernames, in their profile? Often times, especially if I go inactive for a bit, I comeback confused, trying to recognize my old friends and such. In the past it wasn't a major issue since there were Username Change Events with lists. But now with many members changing usernames weekly due to premium it's really hard to keep track of people, so being able to see people's old usernames would be a big help.
BTW: I have no idea about the technical stuff, so if the site doesn't keep track of such things ignore this.