Maybe you don't even need individual user accounts - today I noticed this app to start (and close) different groups of applications. While I don't need it, this may be an alternative to your multiple account approach: http://www.flyingmachinestudios.com/foreman/
Thanks for this! It's a little buggy wrt hiding/showing applications from the popup dialog, but overall it's working pretty well and was worth the purchase. Hopefully future updates iron out the minor issues.
There's a free version on their website (scroll down a bit) if you'd like to try it. It lacks the toggle hotkeys, but it'll let you know if it suits you before buying.