There are a lot of cool materials suitable for making coins, but interesting alloy blanks aren't widely available to mints. Electrum like you brought up is a workable enough material but its just not commercially available. Specialty materials could be done, but it just would have to be very small batches by artisans rather than mint struck coins. I do a lot of metalwork myself and I end up having to alloy everything myself because even though some alloys are just vastly superior in all regards to what we'd consider the standard, they just aren't vanilla enough to be commercially worth it for big companies to change their ways.