If they'd kept the EMH confined to sickbay then Kes' role would be more substantial, as she would have to be the one dealing with medical emergencies in the field, so they could've started to train her up to be another doctor rather than nurse of medical assistant.
Its such a waste as once they got rid of the creepy relationship with Neelix she started to really come into her own, coupled with some serious mental abilities she would have been a serious asset to the ship. Even if they had kept her as a recurring character.
Or better yet, have her leave the ship in a flash of light and then have her reappear on DS9--they knew how to handle recurring characters and make them as interesting as the main cast