Your case seem very rare. You want to have a 4-of-6 multi-sig, but if 6 out of 6 have signed the transaction, you want it to be shown. A quick solution that comes in my mind is to create another 6-of-6 wallet (with the same xpub keys) and move the money from the 4-of-6 address to a 6-of-6's address. If you did that, then in the blockchain it'd be clear that all of the co-signers of the 6-of-6 address agree upon that transaction.