I think the problem is not so much that you need to start at the bottom as that you need to start small. So 8-bit BASICs are good because:

1. they have a fairly small feature set that's not too hard to get to grips with
2. they do reasonably shield you from the layers below
3. you can actually write something useful which isn't obviously just a toy program

Windows GUI programming fails on all counts. Console-based scripting in Python on Linux, say, is probably pretty good on all three.

I think point 3 is important because it means that you feel like you're actually getting somewhere and you don't have a huge mountain of study to be able to write anything worthwhile. [cf the difference between growing and building programs :-)] And in fact point 3 is where your idea of digging out a Beeb or even a DOS only PC fails -- you're just playing with toys, so there's no motivation. Linux is a system your student can actually use (and ideally is already using), and so the student is aware that small stdio utilities can actually do real useful jobs. The Windows universe is pretty much entirely monolithic GUI programs, which is why it's such a nasty place to bring up kids :-)