I'd like an "under shield"... A board to sit under a standard Uno R3 (which would need pins extended downwards).
It would be larger than the R3 layout, and bring all the IO pins out to screw terminals.. preferably grouped in threes..
Each pin would have GND and +5V either side of it so that relay boards, LM35s etc could be readily connected...
I'm building a solar panel controller which will be a permanent fixture in my house....
While breaking out my temperature inputs from the top of my LCD shield works ok:
It would be so much neater to have a base board under the Uno with the screw terminals already fitted in nice groups of three.. +5V/Signal/GND