Hi all,
Here's the final versions of the script I was working on that somebody else might find handy (Thanks to Michael for his help!).
QuickSplit_XYZ cuts an object along an axis defined on the
script command line.
To set it up: add the script to the moi/commands directory,
hook it up to a hotkey in MoI's options dialog, with the script command
< QuickSplit_XYZ X (or Y or Z)>, separate the parameter by a space
from the command. To use: pick an object, hit your hotkey, and pick a cutting
location on the object. It will be split at that location
along the specified axis.
QuickSplit_Angle works the same way, no parameters needed, but will split
an object along an angled line defined by 2 picked points. (pick the object,
hit your hotkey, pick 1st point, pick 2nd point, object is cut.)
Both scripts are intended for use in the Top, Front, and Right viewports.

Paul