Out of all the things they do in FFXIV this nears the top of my list. Possibly one of the top 10 things I want with the game.
Now, my blist was always full. Every week I had to go through it and if I could not remember why the person was on it, the person got off it. However, I know there are a lot of idiots with a lot of characters out there and this would really help that out.
This also solves the problem people have with people having multiple characters. We can get our multiple characters, and anyone who is annoyed by the person has all of his current and future characters on ignore. I know this is a fairly old idea, but it's worth bringing up.