So... Minecraft with 40K skins?
in a world where you can make ANYTHING! ....so long as its covered in aquilla icons....
i think he ment more of the wow professions. would be an interesting idea, you could turn players into vendors then, making the items for sale.
e.g. you can buy an NPC for your storefront who acts as the shopkeeper even while you are offline. its just up to you to keep stocks up and collect your earnings.
then again...that could be troublesome, with hundreds of players all crafting the same thing. maybe a crafting skill based minigame? then the better you do, the better weapon you craft.
but for all that to work, you'd need to make each proffesion a genuine choise that means something, otherwise there would be people mastering everything.
then you run into the problem of everyone's storefront crowding up the place, maybe a 'free market' kind of area, akin to the maple story one would work, where a player goes to a dedicated area to see al the player crafted items. or maybe have them be able to set up shop anywhere, risk being attacked my mobs but be in a better place to provide emergancy supplies.
i hope the above shows you how difficult it is to conceptualy make an mmo, since this is only theorising maybe a 10th of the ingame economey.
mmos are incredibly difficult to make, let alone make right. blizzard are the luckiest SOB's out there.
anyhoo, i have faith in 40k:online