I haven't actually got a Gemini (yet!), but I've been following the project with interest, and I just thought i would throw my two pence worth in. I think most people would prefer the focus to be on ironing out the bugs in the current generation and improving the software, however here is my wish list for v2 - sorry its so long!
Screen 1) 7" 18:9 (as rumoured for Xiaomi Mi Max 3) OR
2) 7.5-7.9" 21:9 Ultrawide screen - to utilise full width of case
3) Capacitive hardware buttons next to screen (Back, home and overview), so software buttons are not required at all
4) High brightness OLED. You could then have a high contrast mode with white text on black, that would consume a similar amount of power, and be readable in sunlight. Maybe.
5) Anti glare coating
I'm not sure about E-ink to be honest. It could be great, especially for web browsing and typing in direct sunlight, but you would sacrifice decent video playback etc. Its also a bit of an unknown - conventional screens are ubiquitous and low risk.
Keyboard and input6) I haven't had a chance to try it yet, but it sounds like they are on to a winner. Perhaps with some tweaks to improve the quality, perhaps adjusting layout based on user feedback as people get used to their devices. Thinner keyboard bezels could improve aesthetics.
7) Keyboard backlight would be helpful. The size of the Gemini means you can easily work on a plane or train, but it would be great to be able to do this without using an external light - I'm not a touch typer - i always have to look!
Physical keyboard buttons for back home and overview android keys (it may already have this with Fn keys?), and other tweaks so that you can use android entirely without touching the screen
9) A built in stylus would be great, especially for using Linux or windows.
Software10) Android - bake into the ROM a UI switcher - the ability to switch apps between phone/phablet/tablet modes. I'm sure once some clever people get xposed running this will work using Phab7, but I think this is a really useful stock feature. The tablet UI for instance is often better optimised for portrait mode.
11) Windows - my vote is to give people the option - if version 2 had a Snapdragon 845, Windows for ARM could be implemented without too much work. You could use the android OS 90% time, and just boot into windows for the things that it can't do.
12) Give away a good few free units to some of the amazing developers at XDA developers etc. As almost everything android is optimised for portrait, touch screen use, I think Planet could use all the help they can get!
Other hardware13) Battery - This could easily be bigger without compromising too much i think, even if it made the device a little thicker. The originally proposed 8000mAh sounds about right.
14) External Camera - Keep it optional - I'm actually happy that this is an option, as I don't see to much point in having one. I may be wrong, but I think most users would carry a phone in addition to this? Maybe it is just me, but without an external screen this makes a poor phone, and an even worse camera, which is exactly why i would carry a phone in addition to this. Even if the camera quality was amazing - you'd either have to shoot blind, or open it up to take a photo, both of which are a bit odd.
15) 4G - Perhaps it is possible that the Gemini can share a phone number and data allowance like the Apple watch does? You could then reply to texts and emails either from either your Gemini or your phone.
16) For V2 does it make sense for Planet to sub contract out the hardware design and manufacturer to a phone manufacturer, like google does with Nexus and Pixel? Planet have clearly spent a lot of time designing this hardware for manufacture, and there isn't really any other way to do it for a device so different from existing ones. It must be blummin hard to make a new device, but lots of Chinese manufacturers make great phones - Planet could give them the design of the V1 device and let them design and manufacture V2 (with Planet in control), leaving them to focus of the software side of things where they can have the most impact.