There is a reason that the most successful businesses subscribe to the maxim that the customer is always right.

I've looked into the suggested systems here, and it seems that there are several exact solutions to the problem, most noteably the Avaya IP Office suggested by TTT.

As a close to exact system, with the only change being having to use the flash hook, I could use the TalkSwitch for a few hundred bucks, saving thousands.

Thanks for the help (at least those of you who tried to help instead of telling me why I was wrong for wanting what I want).