1) If you don't like how postfix is run then feel free to use other tools, fork it, or start your own project. This is open source and you have the power to do it better. If you are indeed right then your project will be successful. Put the money (effort) where you mouth is.
2) You can politely suggest something but you will get a much better traction if you first establish your reputation among people who work on this project by contributing code, documentation, whatever or even simply answering the questions in the mailing list (after about a year it gets really boring since questions are always the same).
3) (IMHO) There is no silver bullet. Git (or any other tool) will not make your code/project better. Moreover you might find that Git (or any other tool) is not perfect and there are problems with it in a particular environment (hint: there is no free lunch). Recognizing the tradeoffs is a very important skill for a software developer. Learn it early and you'll make less mistakes.