Really appreciate the amount of thought into this. I went through some similar designs- I wanted a skinny PDIP size over the breadboard area, but the design we eventually came up with is a 46x20 board that looks a bit like:
************ ************ TinyDuino Board
++ ++
************ ************ TinyDuino Board
++ ++
************ ************ TinyDuino Board
++ ++ (Connector)
-------------------------------------------- (PCB)
| | | | | | | | | | | | | | | | (Pins)
[ ========================= Breadboard with inter-lock notch
So, both a top and bottom connector to have two board stacks. The board can be used to split stacks, soldering breakout, breadboard adapter, or for terminal blocks.
For breadboards it will unfortunately cover up a lot of the space(only leaving two rows on each side), so we'll probably have to pair it up with a medium size breadboard.
Board is ready to go, but we don't have a release date yet.