Hi! I suggest to improuve basic wine prefix manage.
By short: look at cedege.
By detail: the main idea of playonlinux is to manage wineprefix - easy add/easy delete/easy reinstall. Most application can put crap into each prefix, so playonlinux should make this process more cleanly and easy to do.
I suggest to make two hierarchy main window: first level is wineprefix name, second - shortcuts.
First if you try to install some game into prepared prefix like "Diablo II" (Diablo[space]II) you will got some errors, because of [space] in prefix name.
But back to your question. I think most predefined actions outof date, and better and easy way to install game by manual install. I should get abble to run exe into each prefix in one click. Just right click, then choise which exe i want to run within specified prefix. No need a lot of menus and Next buttons. I think.