Glad to read explicitly in the first post that Sailfish is the first priority, not an extra. Not sure if you meant official Sailifsh with AD or a port, but it's already sending good waves. Glad to see this mockup as well! Looks very familiar, it seems that the reference to the Lauta was not chosen ramdomly.

About the metal casing, three naive questions here:
- Does it allow thinner casing than, say, polycarbonate (or whatever was the synthetic material used on the N9, and maybe the Lauta if I remember the pictures correctly), and therefore smaller overall size? The reason I'm asking how it compares to the N9 material is I remember it looked great and felt even better in the hands, it also aged relatively well in terms of signs of wear.
- Does it provide better shock-absorption and therefore better fall-resistance of the screen? Phones do fall, that's a law of physics. But the more they can survive a fall, the more they can fall again over their life. And more falls is better. Of the three questions here, this is actually the most important to me; I would not want to witness such a unique but limited phone break. All my phones so far have been very resistant, never broke a screen, but they were all plastic only (and in general, removable back cover seemed to significantly increase shock absorption).
- Is metal considered by Livermorium an important marketing argument, in addition to putative benefits above? This is not a trap question, marketing is important and I know nothing about it. If something is objectively inferior but makes a device sell better, then maybe it's better to the overall project (but there are limits to the idea, like Android instead of another OS ). If so, is it considered the only material that would make the phone look good, or are there other candidates (like N9 material for instance)?

A little bit surprised, but to be honest I wouldn't even know what would be my preference if I was asked. If I imagine myself thumb-typing on keys that are almost completely concealed by my thumbs, I would assume I need a pretty good tactile feedback and that would be what matters the most.

If keys are dome-shaped like on the N900, and therefore easy to distinguish from top row to bottom row, then I think aligned rows are less confusing; very few tactile information needed to discriminate them and the spatial relationships between keys are simpler, it's just a grid.

Another thing to keep in mind: thumb-typing implies typing not only with the middle of the thumb, but also with the sides just by twisting the thumb left and right without actually moving its position on the keypad. This was perfectly achieved with the N900 and dome-shaped keys, the thumb could just navigate in columns and rows through that grid, sliding in straight lines between the keys. This was a very easy way to orientate it and always know approximately where it was, and one could type either Q, W, A, or S without changing position. I'm afraid a keypad with offset would prevent sliding the thumb and typing four keys with minimal move like this. Would it be harder to type? I cannot tell, I don't know. It probably partly depends on the overall size of the keyboard, keys and gaps as well.

I will trust whatever you guys think is best, you have the experience, but please don't try to mimic full size keyboards just for the sake of mimicking them without making sure it wouldn't hurt thumb-typing experience.