If you're going to make a user-friendly client for nonspecialists, I will suggest the first thing you should do is check to see whether it's on a pristine machine or one with other stuff installed and in the latter case refuse to run, with an appropriate error message. Above all else, Bitcoin for nonspecialists needs to put a stop to the endless stream of newbies having their money stolen, and part of that is making sure people don't put their bitcoins on the same machine they use for other stuff.
(The client should also check whether it's running in a virtual machine and refused to run if so, to guard against a case where somebody tries to run it in a virtual machine on the same physical computer they use for other stuff.)