I've built a set of classes and functions which I use daily at work. It allows me to build CPTs, generate meta boxes, and create option pages in as little as 2 lines of code and saves a ridiculous amount of time, especially for highly customized designs or when you need to add meta boxes to existing CPTs/plugins.
Currently I only have it up on GitHub. I'd like to turn it into a plugin so that I/developers can get updates to it more easily. As it only provides functions/classes and therefore has no backend/frontend, would it be allowed in the plugin repository?
I guess the loophole (if one is needed), is to design a visual editor as well. But I don't really want clients accessing this sort of power, as it could result in explosions.