How about Pershing Square or another common shareholder? If the UST stake is worth $ 80 bn - the common stake is worth $ 20 bn - if the UST stake is worth $160 bn - the common stake is worth $ 40 bn. Seems like a good enough incentive to bring a suit. Pershing Square did it once - if $20 to $ 40 bn is on the table there is a lot of incentive to bring a suit.