posted about wanting an RPG game book that requires
players to write in the rulebook, or paste replacement rules over existing rules, as the players play the game. The example I focused on was the idea of a character class changing as a result of something a player did: the gods no longer have a foothold in the world, so clerics have reduced power or no power, or high-level magic spells no longer work for M-Us.
I kind of ran with this idea and brainstormed particular ways that a D&D retroclone could be redesigned specifically with this in mind. There would be actual rules -- meta-rules -- in the book that would allow research, pacts with supernaturals, or wishes to change the way a character class worked. You could add clerical powers to fighters during play to found an order of paladins, or make a wish to bestow eternal youth on all magic-users.
I sketched out some of the possible rules in a blog post. I think I'll do at least one follow-up.http://9and30kingdoms.blogspot.com/2014/12/rules-are-meant-to-be-broken.html