and other community banks that handle cannabis won't take in this much cash at once.
How about handling the exchange in multiple transactions over a period of time?
They deposit the limit and trade that on an exchange or OTC, repeating the process until you've converted majority of that to Bitcoin.
They will also withdraw overtime to a wallet (preferably hardware, with multiple signatures and backups).
Transaction fees would cost a lot, but it seems a safe bet besides finding a bank to accept the whole deposit at once.