I think something like this is useful at some point, but if I am asking the authors of some modules I would rather like that code get into the main cerberus repo. Having to choose between multiple variants of collision modules each with a different api doesn't help the ease of use.
For things that are not all day functionality I think some easy access to modules would be great. In this case we should also check if there are legal implications if we provide ways of getting uncurated code into the users projects.
I have some HTML5 platform-specific examples that might be interesting to add inside the main repo and not just as examples. Some of them makes the HTML5 work more like the other platforms. This might be things like load/save files, make screenshots, get parameters from the url, and also tools like clearing debug screen and other things. Some might be crap but some of them have been invaluable to me. They also shows users how to extend Cerberus-X.