multi-user by sd card?

its me again

after some experiments with debian im coming back to linpus till there is a real noob-safe distri for the one ,)

as long im thinking bout this concept:

me an my wife have different tastes in enviroment/themes and of course different icq/mail/bookmarks etc

what i was thinking about:
moving the /home/user onto a sd card, so 3 cases could happen
1) no sd card is in, which means its any guest who should have firefox an pidgin (no pw saved of course)
2/3) me or my wife has the personal sd card in, and has the own enviroment

i just wonder, if i mod the /etc/fstab to mount the sd-slot as home, would it behave as i expect (point 1, the guest-feature is not a must, but would be a nice addition ,p)?

thx for any hints

ps: had the custom-dektop-script from this forum running

 

ok, here is my basic idea what i would do under windows, but i donÄt know how to "transalte" this to linux:

into the autostart
check wether a sd is in the slot (maybe errorcode of mount or simply copy a file and grab the errorcode)
depending on the code remount

sounds simple... if id have someclue of linux =(