Bump the power up to 10 watts and use a inbuilt lithium battery pack.
Shrink the whole design down using all surface mount components, even if this means losing the kit option.
Make the design a rugger waterproof unit that you can kick around like a football.
Offer a single lever paddle option
Offer a DCDC converter that can run from 9 volts to 50 volts DC
AC to DC converter that can run from 90 volts to 260 volts.
Use a LCD display
A build LED torch for emergencies, with red as option so it does not destroy your night vision.
Printing in glow in the dark paint.
Support CW keyboard operation.
A Android phone rig control program.
A PSK IMD meter, so you can use the radio as IMD meter for your normal station
Invert the design like the Yaesu FT817 so you can use it backpack or neck mobile looking down on the controls
I think that should be enough, dream on it will never happen now that the KX3 is here.
If Elecraft up dated its KX! QRP rig, what should they add or change?
How do you want tune your antenna?