Even Better: Pseudo-Network Computer
Your general idea is similar to what companies have been promising
with network computers (i.e. give the client a black-box which
"just works" for them).
Perhaps the best of both worlds could be realized: instead of being
a "computer salesman", you sell high-speed internet access (i.e.
cable or DSL) combined with a computer and support. Then, user
machines have a little tiny harddrive which can contain a boot
and swap partition and little else; everything resides at your service
center with drives mounted remotely.
This would simplify things greatly; the customer gets a few different options for a machine (i.e. more money for more RAM/better video card) and the administration/updating would
be much easier. Each different client-machine would mount things
from a different server, so that you can provide Pentium-optimized
The user's data would all reside on their own harddrive, though,
so that they wouldn't be quite so concerned about losing the data.
Given a few more user apps for linux (notably an improved GNUCash (http://www.gnucash.org) and Mozilla (http://www.mozilla.org)), I think an idea like this could definitely fly.