Getting a BP at T5 means you could take the landside shuttle back to T1. With the train system not running for "modernization" they've been running fairly consistent buses. The one benefit is that they run counter clockwise, which means the first stop after T5 is T1. Now you'd still have to clear security and walk over to the Polaris lounge at T1, but it should involve less walking than the T1 to T3 walk followed by waiting for the T3 to T5 bus ride. Either way... it's probably not an ideal situation unless you plan on arriving early enough to spend some quality time in the Polaris lounge AND you don't have luggage to check AND you can check in online/mobile and have a BP before you arrive at ORD.