Have you tried the HNW departments. I have clients who bank with DIB, Mashreq, SIB and ENBD. They all are in precious stones and metal.I never received a large amount in my private account. but regarding business account you are right. it will be very difficult.
anyway, gold + large amount is a no go.
what about payoneer ? do they support large transaction on business account?
Depending on cash funds available if you have 150K to put as your minimum account balance you should be fine.
What licence do you have?