I dont see any problem with what your doing. Its annoying, but all you have to do is simply have two complete minecraft files in different areas, then use the new "Set game's location on hard drive" feature on the new launcher to the one you want. You'd have to do it every time you switched, but its a lot easier then the other suggestions.
Setting up a batch file once to do that for you is harder than doing it every single time? What?
Your jargon lost me.
So my explanation of the fact that the batch file won't break your computer (because technically it is editing a system variable that Windows needs to function, although it's actually not doing any editing) made it hard to use?
Fine, if you don't want to know any of the background information behind it (completely un-befitting of the Bay12 forums, but whatever)
Idiot's Guide to "Automatic" Multiple Minecraft Installations
1) Open Notepad
2)
set APPDATA = wherever/the/data/you/want/this/instance/to/use/is (ex. "C:\Games\Minecraft Folder\data1" )
path/to/Minecraft.exe (ex. "C:\Games\Minecraft Folder\Minecraft.exe" )
(Obviously, change the directories to match -- Encase in quotation marks if there are spaces, and keep in mind that it will make a .minecraft subfolder in the data directory)
3) Save as ANYTHING.bat (make sure to select ALL FILES, for the extension, not .txt!)
4) Repeat as necessary for the number of different copies of the game you want. Obviously, save with a different filename.
5) Run these instead of the launcher as needed.
EDIT: Numbers derped when I added a step.
Note that this will NOT work if you have actually changed the directory that the launcher looks for files in.