Allow the creation of web-hooks on a games configuration page for a particular topic in messaging service. When a string is sent to this web-hook, it will be the equivalent of using PublishAsync with the given topic and string from a normal game server. This would allow more efficient communication outside of roblox servers, currently you have to poll at an interval and this uses up many HTTP requests and is not instantaneous. This would also allow the use of web-hook pushing services like zapier without the game developer having to fork out money for server hosting.
No other special considerations should need to be taken by roblox, game developers should be able to create their own ways to determine if incoming data should be allowed. I could send a json file to my own web-hook with a unique key, or encrypt it a certain way, but the data string sent to the games SubscribeAsync callback should be the same raw data posted to the web-hook.