The general solution for one public IP, but many HTTP servers is reverse proxy server. The 4011 can run containers so if you ask me that’s the best option. In addition to the traditional reverse proxies of Apache & NGNIX, there are more nouveau container-friendly options like https://caddyserver.com and Traefik too (http://forum.mikrotik.com/t/container-traefik-on-rb5009/165849/1)
If you’re willing change the port for your 2nd server, that can work too – just all users would need to use the port in the URL.
Perhaps there is firewall solution with Layer7 if HTTP, or perhaps tls-host= if HTTPS+certs… but not 100% and almost certainly that add more load on than any simple reverse proxy container. And involve a few rules to even have a shot of working. While something like caddyserver.com container can deal with both site in standard way, and likely add ACME-based certs to secure it.