I'm starting to see that all situations cannot be covered by one inventory module. I'm also starting to appreciate the fact that the inventory API is separate from the stock level manager (very insightful).

I only consider myself a hack when it comes to PHP, but I have already started to rework the stock level manager for my purposes (just like you and Ryan have suggested). So far, I can decrement inventory just the way I would like it...but I'm still working on re-incrementing inventory when items are put back on the shelf or when carts are abandoned.

Of course, if I come up with a useful stock level manager, I will definitetly contribute it back for anybody else who might find it useful.

Thanks to everybody who has participated in this thread.