There doesn't seem to be much that they can do to game it as the calculations seem to be based on uninsured deposits. The bank doesn't control how much a depositor places in the bank.
EDIT: I'm not saying the system can't, for a lack of a better word, be gamed, but ultimately that requires action on the depositors end, not necessarily the bank(s).
EDIT 2: Which means that any balance over that 250k in the same category would, in theory, count towards an institution's uninsured deposit balance.
Ha! Of course they do.
All it takes is a letter or phone call advertising a new cash management account that holds overnight treasuries. Customers can sign up and move their $250K+ deposits (which technically aren’t insured anyway) to that non-deposit account.