As I said, I’ve got a VPS. The VPS is not on my local net, but in a datacenter. As part of being a VPS it has a unique IPv4.
My VPN (which I currently use for TCP traffic) is hosted on the VPS, giving me access to (and from) all devices connected to my VPN regardless of whether they are behind a NAT or not.
I’ve also got a beefy server which hosts more power hungry services, though this one is behind multiple layers of NAT. I can forward and reverse-proxy TCP services from the beefy server through the VPN and out to the public net using another server with a unique IPv4 just fine.
What I (and OP) need, is to also be able to forward\reverse-proxy UDP services from a beefy NATed/firewalled server through a VPN and out to the public internet using another server which has a unique IPv4.