I built my own portable mechanical keyboard for precisely this reason; I got spoiled by a nice board at home only to be filled with disappointment every time I went out for a change of scenery at the coffee shop. Now I've got something that almost fits in the pocket, has a nice split angling of the columns, and is designed to work with Emacs from the ground up. (lots of thumb keys)
Any chance you could provide a picture of it or a link to something similar?
Lately I've been using a chromebook with arch whenever I use a laptop ( luckily it's not too often ), and while they keyboard isn't completely awful, going from mechanicals at work and home to a chicklet keyboard is annoying at best. I've been looking for a decent portable mechanical keyboard to throw in my backpack, but so far a densely keyed (not sure if that's the right term?) tenkeyless is the best I've found, and I'm having a hard time imagining a keyboard with all the "extra" keys being almost pocket sized, unless you're bringing back JNCO ;).
It takes a long time to learn since it's a pretty big divergence from the conventional design. It only has 42 keys, but with the fn layer (activated with the thumb rather than an awkward pinky reach you normally see on laptops) you can still hit all the keys you need. The other upside is apart from being much smaller it also means your fingers never have very far to reach, so it's also more comfortable.
I feel like this is the way to go -- It's too much cognitive overhead, IMO, to get used to multiple (very different) keyboard layouts. The Atreus is a nice solution to that, since it's even pocketable. I also disagree with thumb clusters, but that's another story.
(BTW, the article did mention and link the Atreus, so you probably don't need to dance around it like that)
