I think that the most immediate alternate ending for the story would be if the Postmaster and Ratan left together.  This would help to bring about a redemptive ending in that he recognized how important she was to him and how important he was to her.  In both of them leaving together, the ending is one in which there is hope and redemption.  It might help to make the story a bit hollow as the entire philosophical ending that Tagore gives with his own narration becomes null.  Another alternate ending would revolve around Ratan's reaction.  In the story, when the Postmaster gives her money for her time and service to him, she simply runs away after trying to articulate a couple of words.  An alternate ending to this would be that she simply confronts him or even stands with dignity to him, almost conveying the message that she will not lose her self respect or feel ashamed because of him.  This helps to create a stronger vision of Ratan, again something that is not entirely rendered by the philosophical conclusion of the story.  The critical element here is that whatever ending is offered, it has to be reconciled with the human frailty and intrinsic weakness within consciousness that Tagore brings out in his philosophical conclusion to the text.