I think they'd only be able to increase it that much if they increase PQP earning rates on their cards. Right now Delta is 10 or 20 to 1 depending on the card. United is 24 to 1. AA is of course 1 to 1, but their Exec Plat requirement is less than 6x higher than Delta's new Diamond requirement, so it's almost like 6 to 1 given their current thresholds.

My feeling is United would be better off both increasing the PQP earn rate to drive more spend and increasing the qualification thresholds to something in between what AA and Delta is now. People are up in arms about Delta's 35k level. United could position themselves well to snipe former Diamonds from Delta by making theirs around 25-28k while making it a bit easier to earn PQP from credit cards, assuming they want them.