fixing broken plugins/adapting features to other plugins

Hardly a day goes by when I do not have an issue with a plugin, it is broken, doesn't work, has deprecated functions, has obvious bad code, has encoding/encryption, throws an error message on activation, etc, etc, etc. Another has some really god features but the overall plugin is bad or doesn't work. No developer support etc. Others have 10 site limitations, which are very difficult to manage as the creator wants to make more sales because he knows it is hard to manage like this. I have heard other "creators say they have dummy code to stop people stealing their code, all the while most of it comes form wordpress.org. I think what would be really valuable for members is a best practice/how to find and fix plugin errors, how to remove/add features to plugins, tutorial. I think it would make a valuable training for members, any thoughts?