I think a Power Connector shield would be great! It would be wonderfully useful!
Oh the issues with connectors... all sorts of stress of plugging and unplugging connectors really make surface mount connectors less than desirable. If there is some sort of extra strain relief tabs for the SMT connector, that helps tremendously. The preferable configuration may be a through-hole connector.
a) JST connector seems desirable, but which one? Perhaps 2-pin or 3-pin JST-PH connector. A concern with the JST-PH connectors is the height. The SparkFun Through-Hole 3-Pin JST Right Angle Connector
https://www.sparkfun.com/datasheets/Prototyping/Connectors/JST%282%29-01548.pdf - has a 5.00 mm +/- 0.3 mm tolerance (same for the 2-Pin version). The space between tinyduinos is 5.11 mm... the tolerance
could be a problem if the board is to be sandwiched between other tinyduinos. This configuration would be similar to the TinyLily Mini to a JST Power Connector. Of note though, is the stated the Max Height is 6.23 mm. That particular JST connector would not work for a sandwiched board.
b) Right-Angle 1xN-Pin 0.100" (2.54 mm) Female Header flush mounted to the edge of the board so it is facing out and not up. The width of these connectors is 2.50 mm +/- 0.15 mm (according to the specs provided by Pololu's site
http://www.pololu.com/product/2703). This connector choice should have no issues.
c) A DC Barrel Power Jack/Connector such as the Adam Tech ADC-029-1 which is 5.00 mm (with a +/- 0.197 mm tolerance? (If I am reading the spec sheet
http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Prototyping/ADC-H-028-1.pdf correctly)). This makes this option a very tight fit as well, for a board sandwiched between 2 other tinyduinos.
d) The TinyShield Proto Terminal Blocks without the terminal blocks and a Right-Angle 1x2-Pin (or perhaps up to a 1x6-Pin) 0.100" (2.54 mm) Female Header flush mounted to the edge of the board on the open end would be a great configuration. A 5-Pin connector could have GND, VIN, 5V, 3V3, VCCBatt. A 1x6-Pin Connector I have fits perfectly in between the mounting holes. Perhaps sitting the connector back from the edge could be useful as well allowing for a connector to be inserted and hang as little off the board as possible.
e) A shield with just a Right-Angle 5-Pin 0.100" (2.54 mm) Female Header connector (as in (d)) flush mounted to the edge of the board across from the board connector would be great. Perhaps sitting the connector back from the edge could be useful as well allowing for a connector to be inserted and hang as little off the board as possible.