Wy not making a kiosk knoppix remaster in the following way:
-Removing some rights to the default knoppix user, like the su / sudo command
-Removing hacking tools.
-Removing hard disk tools. (partitioning and writing)
-adding flash plugin.
-adding gaim chat client.
-adding cupsd at startup (plus the printer for the kiosk)
-adding streaming video/audio clients with browser plugin.
-very nice 3d gl game support (like HL, UT ecc.)