IMHO even the current 800x480 is quite fine for such a small screen. I'd just like the screen to be 5 inches so that you can really enjoy all the multimedia content on it. Oh, and it'd absolutely have to be multitouch.

I'd prefer single-core myself. Why? Well, I have a dual-core phone from before and almost NONE of the software available for it actually used threading so they only ran on one core. It seems the trend still hasn't changed and all mobile software are optimized for single-core. Thus, a 1Ghz or higher single-core CPU would be a better way to go.

This. But with one exception: when using HDMI output actually use the higher resolution instead of just scaling the stuff up from the phone's own resolution. It's easy to do, yet most companies seem to rather just upscale the stuff and going the lazy route :/

Atm I'd prefer Android because of its humongous amount of software. MeeGo perhaps in the future, but only once it's actually useable for day-to-day tasks for the general populace.

The keyboard could use some work, yes, but I'd like to add a virtual projected keyboard to it: if you have the device sitting on a table or connected to external display via HDMI you could enable an infrared keyboard that is projected on the surface in front of the phone. This would increase its usability by miles.

But oh well, since I am not in a position to actually manufacture the devices myself nor does anyone in such a position wish to listen to female audiences it's unlikely there'll ever exist my dream device.