So I've been working on a project for a Minecraft utility for the last two months or so, and I just updated it, so I figured I might share it and hopefully some of you might be interested. It's called Jetset Minecraft Manager.
It allows you to have separate Minecraft installs that are entirely portable and separate, located where ever you want (the app automatically puts them in a folder at the location of the exe, but you can move that folder and the exe where ever you want, including on a flash drive).
When you first launch JSMM, it'll automatically import the existing Minecraft install you've got in your appdata folder, prompting you for a name. You can then copy that profile into a separate folder, so you can do things like update Minecraft without overwriting the old version, keep backups of your install/world in case you want to revert, install mods without worrying about conflicts or not being able to play vanilla multiplayer, etc. The names can be any unicode character, as long as you want, and it'll be saved in a txt in your profile and automatically sanitized for the folder name of your profile, no worry about bugs or incompatibilities.
JSMM has controls to create, delete, copy, or rename profiles, and a button to open the profile folder for easy tinkering or modding. When you want to play, you just launch the app, click your profile from the list (the topmost item will automatically be highlighted by default), and click "Load Profile".
Give it a chance, and give me some feedback, will ya?