They already did this for pats in T5/T6/sunwell. They all require stuff that only drops from the instance, and the gear at the appropriate level. usually its a BOP recipe and BOE gear, or visa versa. You really dont see that stuff on the AH because of the mats requirements. I think its a great idea and a strong incentive to keep one crafting profession.

I think the main issue with crafting (I do LW/enchant) is that they are all absolutely useless until outlands (where right off the bat you have great enchants/gear sets that arent replaced). For example for enchanting you have +26 AP gloves/bracer, those are best in class for dpsers like hunters. For LW you have 4 set green patterns which are as good as quest rewards or better (esp with set bonus).

They could really make crafting much more viable by having enchants be able to put onto a paper or something that you can sell on AH (as mentioned at blizzcon last year), and increase the item level for crafting to make it on par with quest rewards that you'd get around that level. Typically when you level LW you are 10-20 character levels behind, ie the stuff you need to make a item comes from a level 50 mob, yet the item is level 30 or 40.

But the main thing: Stupid people pricing items for *less* than it costs to make, even end-game stuff. Example: riding crops. Can't sell them for more than the cost of a primal might, people complain high and low. So we end up taking a 20g hit every time we make one of these.