Tiny Tim dies of his disease anyway. Scrooge’s good tidings come too little too late for the long suffering boy. What is he suffering from anyway? Rickets? Tuberculosis? Renal failure? It’s not like modern medicine’s been invented. Ain’t no such thing as antibiotics yet. “Tiny Tim, who did NOT die…” Everyone dies, Dickens, just a matter of when.
Scrooge becomes like Marley anyway — a wandering ghost with chains and lockboxes and safes strapped to him. A lifetime of greed and covetousness doesn’t make up for a few years of charity at the end of your life. The Powers That Be can’t ignore the years of suffering of the citizens gouged and foreclosed on before Ebeneezer got his “epiphany”.
Scrooge is committed to a mental institution. He wakes up one day with a total shift of personality, claiming that he can see ghosts and they showed him the future and events of the present he shouldn’t be able to view. How would you react? This goes one of two ways. If he proves it by revealing knowledge of Bob Cratchit and Nephew Fred’s house, having never set foot in either, they burn him at the stake as a witch. Otherwise, he’s just thrown in the loony bin (which is an awful awful place during this time period). Who signs the papers? His investors. Scrooge must have compatriots and associates in the financial industry. Once they see him trickling money out of his pockets with no ROI, they’re going to put a stopper in that right quick.
Scrooge never leaves his nephew Fred alone. He becomes an uninvited guest, trying to make up for years of neglect in a few years. He and his wife start to resent him. Resent turns to hate. They eventually spurn Scrooge, and he goes right back to a bitter old man, finding his well wishes don’t stop people from hating him.
Bob Cratchit, while he now works for a more hospitable employer, never gets out of the financial situation he’s in. He’s still a clerk (not terribly skilled labor) with five children. His children all grow up to have similarly dull lives, married to spouses without means. Tiny Tim, who may or may not have permanent effects of his illness that required constant home care, is still smaller than average due to malnutrition and must rely on welfare of the state (which I don’t think exists in this time period). They’re all one toothache away from the streets.
Scrooge dies in poverty, having given away his vast fortune.
Scrooge finds the grave-robbers he saw in the vision from the Ghost of Christmas Future and kicks their ass. He has them arrested and sent to jail. This is the happiest ending I could think of.