You can easily forward arbitrary IP traffic if you get an additional IP for that VPS. Then you add the IP as your own on the local end, and set up routing like

ip r a 1.2.3.4 via 10.10.10.10 dev wg0 where 1.2.3.4 is the extra ip, and 10.10.10.10 is your local wireguard address.

With just one IP, you can forward ports over wireguard with iptables, but I failed to do that correctly.

Now I’m using xinetd to forward traffic from external ports to Wireguard with a single IP. iptables would be better but I ran out of patience.