That 36 month seat lock is only is you want to move from one FO position to another, it doesn't keep anyone from upgrading.

It's debatable how long it would take you to upgrade if you joined as a FO. I personally don't think you'd wait more than a few months because large amounts of the FO list are about 1000hrs shy of ATP mins. I say try for the street CA position and let them know during the interview that if they decide to turn you down you'd appreciate a FO position...hell that might win you the CA spot right there!