This is what I'd consider if something like this came up at work, and there was too much crufty old code in the 32-bit systems to get management to accept updating the whole thing to 64-bit.
Change it so that what is listed on Nasdaq as BRK.A is not actually BRK.A but rather 1/2 BRK.A. So when Nasdaq says BRK.A is $X it is really $2X, and when they say N shares traded that day it was really N/2 shares. Only allow transactions that involve an even number of the 1/2 BRK.A shares.
Hopefully the code to handle all that would just need to be in the interfaces between the 32-bit systems and the rest of the world, and should be a lot less work than changing the whole thing to 64-bit.
Change it so that what is listed on Nasdaq as BRK.A is not actually BRK.A but rather 1/2 BRK.A. So when Nasdaq says BRK.A is $X it is really $2X, and when they say N shares traded that day it was really N/2 shares. Only allow transactions that involve an even number of the 1/2 BRK.A shares.
Hopefully the code to handle all that would just need to be in the interfaces between the 32-bit systems and the rest of the world, and should be a lot less work than changing the whole thing to 64-bit.