Sometimes it is kinda fun and fulfilling to repair thing's. If it don't take a long time or cost much to repair, I enjoy repairing things.
Oh I understand that. I've got several garages full of things I'm going to repair some day.

However, self-sewing a ratchet strap, I just don't know. Sure, you could do it. What strength thread would you use? How would you know the repair is gonna hold the load? If your load falls off your trailer and kills you, will your insurance void its coverage? Etc.... It's just one of those things I probably wouldn't attempt a repair on since the cost of new is so darn low. I'd keep the mechanism if its in good shape, and use the old strap for firewood log duty until it got too abraded. Or a tire swing.