I had booked a flight within the past 6 months or so where it included AA Codeshares on CX. They accepted a voucher for partial payment but did do the 'charge in full to CC, refund when voucher was received' song & dance. I wonder if they only do that on codeshares in excess of the voucher amount. Not sure how I was able to do it, but I definitely recall doing exactly that and being charged in full in advance and then being refunded when the vouch was received & processed.