I do not suggest doing that. As John EB indicated, the installer will uninstall the previous version first but leave certain things, like additional content behind. Then, when you go to install the additional content for the new version, most will already be there and MEP detects what is not required and does not install it again. No duplication. The files are under folders that are shared with each version so as to avoid duplication. Uninstalling the previous version before installing the previous version will just give you more work for the same disk space. Nothing to be gained; potential problems if you don't do it correctly.
I'd also appreciate the option to revert to a usable form of the program, literally all the updates do is make you arbitrarily leap through extra hoops in order to complete the same action which was done effortlessly before the new update.
I'd kill for the chance to go back to a previous version of this program, my life is hell now that the simplest actions require double the effort.