I've been to checked-baggage stations, lots of times, and have seen quite a few un-staffed stations as well. WPK is staffed, with baggage handling. The question, it seems to me, is passenger count at these unstaffed or non-checked-baggage station stops. If you typically have a small passenger count at a particular stop, then there shouldn't be that much of a delay. Perhaps add one person to the train crew to handle the baggage for the whole trip if you don't have somebody there to start with. Even two people, per train, is still going to be a heck of a lot cheaper than the huge overhead of staffing a bunch of otherwise unstaffed stations, plus all the additional equipment overhead at those stations. If you regularly have enough passengers at a particular station that you are delaying the train by 5-10 minutes, then it's time to consider staffing the station stop. But be flexible about it - could you hire some part-time folks to act as baggage handlers without having to put in the additional "conveniences" at that station stop (for ticketing etc.), or could you just add part-time baggage handlers and nothing else.
The only real problem I see there is what do you do if baggage arrives with no passenger to claim it, or what do you do with a bag erroneously offloaded at that stop? You've got to have some way to securely store it. You could probably eliminate that problem if passengers would be immediately directed to the baggage car (perhaps put it at the back end instead of the front end) to claim their bags, with baggage handling personnel and perhaps an AC to assist in expediting it, matching claim checks, etc. If baggage handlers would be given baggage check numbers, and only bags matching those numbers would be offloaded, with all other bags remaining on the train, then no unclaimed bags would be left on the ground. And while the AC and baggage handlers are handling those bags, the Conductor and other OBS folks could be organizing and entraining new passengers. And if they had blank baggage checks, they could do a quick job of putting station IDs on those checks, putting them on the bags, and giving the stubs to the passengers entraining. AGAIN, this is for LOW PASSENGER VOLUME stops, with just a low typical passenger count. That's the only way this could work.
To save a little time, you could offload the passengers at those stops, then do a quick re-spot of the train to put the baggage car where the offloaded passengers were. The baggage handlers would already have the bags tagged for that stop ready for claim check verification and offloading.
The bottom line, I think, is that they could make something like this work if they had the will to do it. And again, this would be for station stops with a low passenger volume, where it is manifestly a huge waste of money to staff a station.