If you're asking for an official plugin/addon framework, that's not going to solve the problem and in reality we'd just end up like World of Warcraft. You'd get quality of life UI changes and some of the combat stuff like ACT and Cactbot at the very best. You wouldn't get XIVAlex or NoClippy. You wouldn't get any texture or model swapping for Viera hats (or the lewd stuff that some people enjoy).