I think you could formulate your request better or at least it seems better to me. What about just offering these names to players who want to take them? That would make more sense then simply deleting them. Then if old player comes back after 6+ years, he can still use his acc/name if somebody else didnt take it.
Also, you should specify what you want to be deleted, acc name or only dplogin name/names. IMO, deleting acc names is bad move, but dplogin names is fine, as long as there is a longer protected preiod of time in which this name cannot be taken from you. And i assume you meant dplogin names.
EDIT:I thought of some flaws in this, i am pretty sure they were mentioned before but w/e.
The main problem i see, is in deleting "known" people names, for example my friend selda, he did quite some contribution to the game, made some maps, guides and is pretty well known (to some extend). He didnt play PB for 3+ years, but still has maps which have his name.
Now, if someone took his name, i would be kinda mad, because he is my friend and i dont want someone else running with his name, but thats not the main reason. He has some maps in which is his name, now if someone took his name they could start claiming that they made these maps etc. and there would be no way of proving that they are not.
My suggestion is to give people who played long enough immunity in deleting their names. Or we could give them partial immunity, which would protect their "main" name and could never be deleted.