This product has obviously struck a chord in many readers, hence this very extensive discussion.
Perhaps it presages the convergence of the laptop and tablet form factors. I hope Apple considers this approach and introduces a product that also appeals to the market segment that would buy this kind of product.
Here is what it could have:
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Aside from replacing the mini DisplayPort connection with Thunderbolt, what you describe is already pretty much exactly the Surface Pro hardware.
The main difference is that Apple does not have support for touch, or the option to run tablet applications built into OS X like Windows does.
A mechanically attachable keyboard (NOT magnetic) that would give the device rigidity when used as a laptop.
The primary issue is not rigidity, it's weight - the device is top-heavy.
A laptop has most of its weight in the base, but most of the weight in a tablet is in the "screen".
The only way to really offset that properly is to have a large base with an extended battery, but then you're basically doubling the thickness and weight of the device.
Intel did show off an interesting prototype last year that used electropermanent magnets, and "Smart Frame" - switching between a near frameless display in notebook mode, and thicker borders when used as a tablet.
https://www.youtube.com/watch?v=nG8CPaX1PxQ
But you can see that with the thin base they used, it's not very well balanced, and the hinge is nowhere near as solid as a proper notebook.
Really, I think it's all about the mindset you have.
The Surface is primarily meant to be a tablet, which can also work as a notebook if you need it while you're at a desk.
Using a detachable keyboard is never going to be a great experience on your lap.
If your main interest in it is to try and replace a MacBook, you're looking at the wrong device.
But the fact that it
is a tablet means you can do a lot more with it than a traditional notebook too - especially if you're an artist.
I have a Logitech iPad case which has a stand and it's really nice. But I actually don't use it much because I'm usually just holding my Air in my hand. As far as Mac keyboards, I have no issues with the current design, don't experience the problems you do. To each his own, I guess.
Using touchscreens vertically is usually quite a bad experience - but if you use your tablet for video playback, or if you're at a desk, it's very nice to have.
Even the best cases pale in comparison to the Surface kickstand - and the fact remains that you have to use a case with the iPad to begin with.
Adding a case completely eliminates the weight and thickness advantages of the Air.