Which happens already. PF's that allow arbitrary ilvl requirements, FC's that won't let someone in on Coil unless they meet certain requirements in excess of dungeon requirements. Even without a specific iLvl listed, even a quick examine can allow someone to gauge pecking order. Guess what happens when someone spots an i70 belt? Noob-boot! Go farm Myth.
Lets forget that there are actually iLvl requirements for going into a dungeon, but being held out of Turn 1 until you're 10 levels over the entry requirements is shifty no matter how you look at it. That is assuming, of course, that the 'team' didn't set the entry requirements to a threshold where a party of minimum iLvl can't complete the dungeon. Now that would be shifty.