As I understand, this is the topology you'd like to achieve:
If so, I've tested it quite extensively but was only able to get communication working one way (IPsec → RUT956 → OpenVPN client). I could have missed something in the firewall settings, however, it requires some more experimentation. It's most likely related to the way IPsec handles routing, as there is no entry for IPsec routes in the routing table. That is most likely why OpenVPN → RUT956 → IPsec does not work.
The most important thing to keep in mind with a setup like this is to push the necessary routes to the OpenVPN clients and add the needed subnets in the IPsec configuration.
If you manage to get it working, let us know!