Isn't forced limber accomplishing that as well? Keeping the artillery from firing for a turn?
Seems to me that limbering is a more "period appropriate" result of intense fire. As far as unlimbering in the same spot, it seems as though what is reflected is the movement within the miniature base's footprint. Our miniature cannons aren't showing where every gun, limber, caisson, horse, and gunner is located...they're somewhere within the area of the battery's base footprint. So even though the miniature limbers and then unlimbers in the same area on the table, this could represent alot of movement and adjustment of gun positons in that area over a space of time. And with the games turn by turn system representing things that are actually happening simultaniously, it makes sense. That limbering could represent the unit limbering, getting out of the way, and unlimbering again in the same relative area. Or it could represent gunners ducking for cover, or pushing their guns around.
In the end, just as the miniatures themselves represent all the things that make up a battery, the forced limber rule simulates a
number of different actions by that battery under duress, while maintaining the period "flavor" and not cluttering play with a number of different rules for slightly different reactions to being under fire.
At least, that's my interpretation.
-Scott