Storage requirement would depend on DPI. You're 'only' looking at ~10PB at 600 DPI. Then again you'd expect most everything to be procedurally generated anyways...
I don't see what your example has to do with multitasking. What you're asking for is a way to manipulate system settings from custom apps -- having the settings app run in the background just saves you a few 'clicks'.
Well not necessarily. If the 'sugar on a stick' build expects to be able to write to the stick, you'd need to add something like UnionFS in order to be able to run it from a cdrom. Not to mention that you'd need to setup something to keep users' settings in between reboots (e.g. a usb stick).
There isn't anything in the Toyota's owners' manuals about using glue as engine oil either. What's your point?
"The pathology is to want control, not that you ever get it, because of course you never do." -- Gregory Bateson