>>42500871
Strictly speaking, what we call fillies and colts are more like yearlings, and 'teenage' ponies like this one are the real fillies and colts.
Reading is a lot of fun and everyone who fancies themselves capable of rotating the imaginary apple should be doing it. Fanfic is fine, but there's a whole lot of garbage to sift through to find anything worthwhile. If you must, you can pick up any decent book and simply imagine that the characters are ponies. I do this involuntarily.
>>42356964
This idea is shit, I think the Renegade Games ttrpg does an alright job with interesting mechanics, they even have a Knights of Canterlot supplemental book if you suck and want it to be more dungeon crawl-y d&d stuff. Any changes you could want can pretty easily be homebrewed.