I'm trying to book NA (west coast) - Australia. My preference is a direct flight, and I can find plenty of availability on the return but not on the outbound. One option is to purchase a ticket one way , or maybe use miles on OW. I realize that US doesn't offer one-way *A awards.

But another option that I like better is booking a leg of a future trip as well. I know after my trip starts that I wouldn't be able to change this return leg.

Example:
SEA/YVR/LAX/SFO - SYD Now
FRA/MUC/KRK/WAW - SEA/YVR/LAX/SFO Future

I believe that I'm prevented from having a stopover on the EU leg because this will be an open jaw ticket.

Any other rules I should keep in mind?

One additional "bonus" here is that this will force me to get the outbound part of the future trip planned much earlier than I would normally do.