has anyone ever been successful in booking Emirates mixed cabin ticket with JAL miles?

AAA-DXB : available in First
DXB-BBB : only available in Business, no First cabin

the only option i am given by the JAL customer service phone agent is to book it as separate tickets, so two separate PNRs, and I want to avoid that.

I try booking this mixed cabin ticket online using their search engine, and it cant mix and match either.