YES! That's a great idea. Though it should only become available to purchase after a set time period... e.g. 3 months after release. Just so people can show off their items before everyone else is entitled to them too.
That's what they did with Infamous. The blades skill was for pre-orders only, but was made available for everyone eventually.
f they are going to let people buy the pre-order items as DLC I think it should ONLY be available to people who pre-ordered the game.
This is what they are doing, the items will not be on the disc after all.
They could have a key with your pre-order that unlocks items from whatever vendor you bought the game from, and it would also unlock the ability to buy the other items. Again I don't like this at all, but it is better than anyone being able to buy it and killing the whole point of showing off who the "early adopters" were.
This sounds like BC2, where everyone gripes about not having the one gun that they claim is so overpowered. It should be available to everyone at some point. Who cares who got the game early. Is it that, without leader boards, you need something else to say makes you better than any other player?