While I'm not necessarily opposed to this, I do wonder who this solution serves. No single craft requires more than 8 components, which is allowed in a single trade, along with gil. And the trade system currently requires not one, but two confirmations of the exchange by both parties. I realize you said a few high level crafts, but why can't you split this into several transactions between you and the crafter? I.e. materials for item 1 plus agreed upon gil, materials for item 2 plus agreed upon gil, etc.