I want to start my process by taking a high-level look at the design goals I’m trying to reach with a custom set of rules.
1. CUSTOMIZABLE: Players should have a lot of options when creating and leveling characters to customize them in various ways. The difficulty here is making those options play well together and not requiring players to sort through hundreds of differently powered choices in order to build a character that can hold its own in, and out, of combat. A player should not have to find the right combination of options in order to avoid a crippled character, and players should not get to pick combinations of options that lead to “super-characters.” I’d like custom content to be easy to generate, whether that’s custom classes, skills, feats, races, spells, divinities, etc.