And chorded keyboard on the back please. It can be used as universal back buttons. With side buttons (like L, R) it would be more versatile, especially as gamepad.

And I cannot promise that I will ever buy your keyboard, because i prefer n9 and meego than some bulky phones with android/sailfish.
Meego Harmattan has perfect look&feel for me. I would like to switch to n950 but only half of storage or RAM, and prices are insane.

But maybe if both Lenovo (with Moto Mods) and you will success (with keyboard) then Lenovo will release more compact moto-z and you more compact keyboard. Anyway, good luck!

weird. So, most of the people are lefties?

I take it you mean left-handed as we do not like talking about politics here

I, as a right-handed person, would naturally prefer cursor keys on the right. But, like juiceme, I am not particularly bothered.

It's just habit. Maybe all PCs have arrows on bottom right, so user will look for bottom right by default...

That's what I thought, too. The arrow keys on the left make more sense as a D-pad for playing video games, arrow keys on the right resemble the layout on a computer keyboard. In the end, though, I don't think it really matters which side they are on a mobile keyboard, because although you have a dominant hand I doubt there's something like a dominant thumb.

Sure, but what is going to feel the most comfortable and natural?

Using the arrow keys on a PC keyboard is with your fingers, D-Pad on a gamepad is with your thumb.

Since this is likely to be used with your thumb I would expect on balance that more people would feel at home with a D-Pad style arrangement. OTOH the subsection of people who are n900 owners but not console gamers would probably be more at home with the n900 layout.

No doubt this is one of those ergonomics factors where you're not going to please everyone

EDIT: Third alternative: TV remote, which i expect people would use with their thumb in their dominant hand...

Finally this is becoming reality: Hardware Keyboard for MOTOROLA Moto Z, via Moto Mods. So far things are looking very promising but I have two things in my mind:

1. Size
Moto Z is pretty massive phone (153.3mm long) so it can be hard to reach the buttons in the middle of the keyboard. I did a DIY qwerty slider Android phone with Xiaomi Mi4C (138.1mm) and iPhone 6 (138.1mm) keyboard case. For my hands the length was absolutely maximum. Anything longer would have been too much. Now I'm using my Droid 4 daily and the length (127mm) is comfortable.

Because of that I'm suggesting to split the keyboard. Something like these: LG Protype, Dell prototype. In the middle there could be touchscreen, touchpad, speaker or extra buttons (for camera maybe?). It can also just be empty for lowering costs.

2. Software
Moto Z is a Android phone. It is possible to port Sailfish OS to Moto Z for example but it is not easy job. Like r0kk3rz already pointed out that Moto Z family is lacking CM13 ports. (Even Droid 4 doesn't have Sailfish OS port even though it has good CM support). Another thing to worry about is how the Moto Mod will work if we ditch Android? OS development will need special support.

Anyway I hope this will become reality. Keep up the good work!

Yes, thumbcontrol is to be concidered as standard way of using a small kbd.
If you think about it, an arrowkeypad in center of a split kbd would fit left and right handed people and grant more grip and possibly even onehanded use?
Has it ever been tried before?

EDIT, searchengines reveal some virtual attempts:

Offtopic, but I'm currently doing Droid 4 port. Plan to post it once the basic things are fixed (currently missing sound input and camera at least).

The ID, layout and structure has been finalised today. I will share more info later.

The device will be produced in one of the Foxconn factories, I hope that can assure quality concerns.