Origin Access and Playing on Mac

@SquiglyBoot  I've never heard of anyone doing this, although I'm sure you're not the first to try.  In theory, if the packs you own are listed in your library, they should be available for download once you have the base game installed.  In practice, this is Origin we're talking about, and anything's possible.  So unless someone else has a better answer, I'd recommend contacting EA customer support (https://help.ea.com/en/contact-us/) to ask whether this would work.  Hopefully someone on that end will know the answer.  At the very least, if you buy the base game but can't use your packs after all, you'll have grounds to ask for a refund.