My issue was you claiming "if the game lets you enter it's not a problem". Which is why I posted that example in my last post, which you didn't comment on for some reason, about Queueing as a tank for level 60 dungeons with full crafting gear and healing accessories on.
http://i.imgur.com/6GJ85IT.png
This is a tank queueing for a dungeon wearing all crafting gear and healing accessories and level 50 weapon going into level 60 content. The game let me do it. So I guess it isn't a problem?
You believe if the game let him enter then there is no problem and that there is only a problem if he changes gear inside the instance, but in the end you are just ignoring the fact that the reason for this thread is the fact that he could actually queue with that weapon (I checked on my BLM and equipping an i110 weapon only brought me down to i240), or he could switch to it inside the duty, and
BOTH scenarios are a problem.