Tailscale with exit-node and other vpn for outgoing connection

Hello everyone,

I would like to connect a Raspberry Pi to a wireguard VPN (Mullvad or IVPN or manually configured Wiregaurd), in a way that all of the outgoing traffic is going through that VPN. Then I would like to use tailscale on it and use it as an exit-node for all my other devices so the connected devices to the tailscale network use the pre-configured VPN on the exit-node. I can do that with a virtual machine, where the host is connected to the external VPN and the VM is the tailscale exit-node. However, this has a lot of overhead and I am sure there are more elegant and light-weight ways using networking. Has anyone done such a thing and could share how it can be done? Any ideas or further reading resources is also appreciated.

Thanks in advance for any answers!