Is there a reason why cannot use the existing Perimiter Check Point as your VPN Termination point?
That way would be the star community with the existing Check Point as the Central gateway and branches as the Satellites and just work.
Other Potential solution which would be a bit of cheat but would mean don't need to encrypt/decrypt on the existing Check Point Cluster,
Deploy the NEW VPN Check Point Gateway on a DMZ off the existing Check Point Perimeter.
Use the NAT option so that NAT the new VPN Gateway behind a Public IP on the existing perimeter for the purpose of establishing VPN.
Default Gateway would be the DMZ Interface of the Firewall.
Check Point Firewalls on the SAME Management would see the NAT IP so would connect. Non-Check Point or OTHER Management boxes simply tell them the NAT IP and will be fine.
If is currently a different ISP circuit used for the VPN then as the VPN Gateway IP would be known then could place static routes on the existing permiter to send traffic out over the VPN ISP Circuit. Obviously move the circuit so that IP range goes to the existing Check Point box.
Obviously would need to pass the Encrypted Traffic through the existing Gateway but not Encrypt/Decrypt
Used a similar topology for another customer (without the other circuit) for another customer using Cisco Branch Routers and a Cisco Router for the VPN Termination.