Add the ability to share an AP installation (i.e. resources, images, etc.) between two OSes (in this case either a 32-bit or a 64-bit Windows boot).

Implemented. Preferences→Other has a checkbox. Setting that option will ask you to find the Application Data folder of a previously-used instance of AstroPlanner. i.e. if you want to connect instance B to the application data of instance A, then (a) run instance A and use Help→Where's My Stuff to find the location of Application Data, (b) run instance B and use this feature to select instance A's application data.
NOTE: Instance B _must_ have read/write access to instance A's folder. This might be a problem in both Mac OS X or Windows.