Instead of having to depend on the TinyShield Protoboard, why not have a TinyDuino Breakout board.  It would basically be a TinyDuino, but all of the Arduino digital and analog pins would be laid out in a breadboard friendly layout.  The board would have a socket that would allow plugging in other Tiny boards.  This would make it easier to prototype, and then when ready for the real thing, just swap the breakout board for a real TinyDuino and a protoboard.

Alternatively, the breakout board could just have the breadboard friendly layout and a socket, but no built in TinyDuino processor.  This would allow for a TinyDuino to be plugged into it to provide the "brains".  But this would require the TinyDuino to have an option for having both top and bottom connectors, like other Tiny boards.  Not sure how doable that is.  But again, it would make it super easy to prototype using the TinyDuino and other tiny boards.

-Mark