You're right - you can only get lounge access if on a same-day international trip. One suggestion would be that you purchase a one-way refundable international ticket for late in the evening and you use that ticket as a way to get lounge access before canceling later. (Heck, if you're gonna do it, book a flight in F so you can use an IFL.) It's sneaky, and if you wish to do it, I'd suggest you book with another *A carrier and not put your MP# on the reservation so you're not flagged for being on two different *A flights in the air at the same time.

Personally, I'd prefer the museums mentioned previously.