Check Point has a Mirror and Decrypt feature from R80.20 and up.
With this feature configured, you can either mirror traffic unencrypted or encrypted to a specific port on your gateway.
It is meant for a third-party Recorder or Packet-Broker that operates in monitor (promiscuous) mode to accept the mirrored and (possibly) decrypted traffic.
That means it won't work for your desired use case.
You realize Check Point can do App Control/URL Filtering too, right?
If you're having it decrypt the traffic, why not have it perform access control and threat prevention on it as well?