Having just ordered a Jolla I feel entitled to share my opinions. :P

For the sequel:

• 720p display at same size
• Carl Zeiss (or similar) camera lens at same size
• USB OTG and MHL support

Apart from that I can't find many downsides to the current design, I don't want to force a redesign and to impact battery life substantially.

For a low end device, however, I would like to see a return to the dual-slider form factor made famous by the N95 and N86. There is still a gap in the market for smartphones with a traditional number pad, and I'd love to see Jolla fill it. As for the specs:

• 640x480 screen, 3 inches (non-touchscreen)
• 1GHz single core
• 768MB RAM
• 1500Mah battery
• Customised build of Sailfish