With two VPN clients running on the same pfSense ?
I didn't really insist when testing (things start to behave very bad).
I'm sure that a first VPN client can used as the 'gateway' for a second VPN client on the same device, but you probably have to set them up the old way : manual config file creation and all that. That's not possible on pfSense.
I hope to be wrong of course.
What was possible :
Setting up a pfSense VPN client to 'some' VPN-ISP, routing all outgoing traffic over this connection, that's classic and works fine.
Then I activated a VPN client on my NAS, used 'another' VPN-ISP, and that connected also "just fine".
Now, I had a tunnel over a tunnel.
As I was using some web https sites to test, I actually had a a tunnel in a tunnel in a tunnel.
Btw : you go beyond what is needed to protect the launch codes of the nukes .... are you sure you need this protection ?