use Multisig function on Bitcoin Core RPC in an internet trade?

I’ve craeted a small on-line trade primarily based on Bitcoin Core. The options on this software are:

1. Person ship request to get a brand new deal with, and the Bitcoin Core generate a brand new one with outlined passphrase.
2. Person can obtain BTC on his personal deal with.
3. Person can ship BTC from his personal deal with, and for this objective, I’ve used sendtoaddress after unlocking account with walletPassphrase.

On this state of affairs, there may be one difficult passphrase which is ready to unlock all accounts. However after studying about multisig function, I thought of implementing a state of affairs on this regard on my software. However there are some questions in my thoughts:

1. I’ve used a set passphrase in my codes whereas sending transactions. Relating to to multisig ideas, I want to make use of totally different non-public keys to signal information as an alternative of utilizing a passphrase to unlock that account. Am I proper?
2. Because the operation in an internet trade must be do routinely, I feel I’ve to make use of all required non-public keys within the closing step of my codes. On this case, I feel I didn’t add any new safety mechanism to my software as every thing is positioned beside one another. Can I cound on safety influence of multisig accounts in my software in any respect?

I hope you may assist me so remedy these points in my thoughts.