Hi Marco, you can get the center of an object's bounding box using script - that's actually how the Move and Copy commands do it currently, by this line in Move.js:
    basept = objects.getHighAccuracyBoundingBox().center;

Maybe I'm just not understanding what you're asking about though - I thought you were looking for a way to use the Transform > Move command and have the base point of the move be the bounding box center... That's what the option I showed above will do.

- Michael