having no contact to another potentially insecure operating system running on the same computer
Are you implying that Linux is not potentially insecure? That is as ignorant as the "Macs don't get viruses" statement I hear from 70 year old ladies. IMHO, Linux is a bad choice for someone who is not savvy or experienced with it. I agree that what you are proposing is a good idea, but could be disasterous for non Linux users. I look at Linux as the OS that assumes you know what you are doing. As the teacher of my first Unix class told us "Unix usually wont stop you from doing something stupid."
Not promoting Windows or any other OS (I like Linux) just poining something out.