Little more than thinking out loud (because I haven't thought the idea through very far), but Amtrak doesn't actually own many of the actual stations. I am not sure that the local communities would have sufficient incentive to do so, but they should certainly be free to provide (pay for) personnel for checked baggage service at their local station. This could entail the city paying a portion of the agent(s) salary, or even a city employee (in cooperation with Amtrak, obviously) performing the task.