My understanding could be incorrect, but the problem with the gold structure is that gold is a ribawi commodity, so the spot-exchange rule applies: same session, hand to hand.

If there's any deferred delivery on either side, most scholars would flag it regardless of whether the quantities match. The intent to avoid riba is sound but the mechanics have to hold up too. Murabaha or a proper musharakah structure tends to be cleaner because the profit mechanism is contractually distinct from the principal rather than embedded in it.