Currently if one wants to discover available network services like RPC or REST you need to know about http://monitor.cityofzion.io/, https://happynodes.f27.ventures/ or something alike.

A solution to discover such services via the network would be to extend the VersionPayload with RPCPort, RESTPort and Websocket port (the most common ones currently missing). Then turn the Services into a flag that indicates which services are enabled.

This allows one to connect to the network and discover available services via the nodes (through a combination of PeerInfo requests and VersionPayload's). The aforementioned websites could also discover more available services improving the overall user experience.