I know of a couple of ways around this on a few different airlines, but neither are earth shattering.
AA--I use telephone check in and then call an angel at the ORD Admirals Club and hope that she can get me on the waitlist. This has not worked since the angel in question was bumped, nor since I don't really have legit access to the Admirals club anymore

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US--since I fly from PIT, I'm at a disadvantage from the get go. However, I work right by the airport, so if I'm really in a pinch for the UG, I'll drive to the airport at lunch (let's say for a 5pm flight) and check in/waitlist myself, in the hopes of beating out folks checking in in "spoke" cities.
I don't really see a foolproof workaround, short of showing up as early as your airline will allow.
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Saving the world, one clue at a time.