Route traffic through 2 Fortinet FWs and IPSec tunnels

Dear network processionals,

I was trying to figure out how to provide access from office network  to a remote server through 2 firewalls and 2 IPSec tunnels and it seems I don't have a solution.

I attached the diagram in hope it will be more understandable.

I have an IPSec tunnel between the office FW (Fortinet) and Data Center (DC) FW (Fortinet), so all DC resources are accessible from the office. In the DC, in its turn, I have another IP Sec tunnel to a service provider and a remote service is accessible from DC.

I'm limited seting up one more IPSec tunnel between the office and remote server and I don't have access to a remote FW in order to make any changes.

Setting up  Virtual IPs and NAT on the DC FW can be a solution, but it's not clear for me how to configure it.

Could you please advise me how such access (from office network through DC network to remote server) can be organised?

If any additional information is required, please let me know.

I will really appreciate your help.

Thank you in advance.