Right - by "hardcoded", I meant via #defines at the top of the sketch as opposed to making it settable via the user interface (or jumpers). The same thing applies to 12 vs. 24hr clock and degrees F vs. C. If this was a "blackbox" alarm clock, I'd have to make these user settable but I'm assuming anyone interested in this shield would be willing to upload the code themselves and quite likely tinker with it.
As for the display size, I want the shield size to match the common Arduino form factor for my primary application but I did include "expansion" vias placed on 0.1" centers so that it should be pretty easy to connect the shield to a larger display (with the 0.56" display not installed). The controller chip can handle up to 40 mA per segment but I believe it would be possible to drive higher powered displays with external transistors. That is something I do plan to test in the near future.