Whisk together shallot, vinegar, mustard, and honey; gradually whisk in bacon fat and 1/4 cup oil. Crumble in bacon; season with salt and pepper and set aside.
Drizzle cabbage with oil; season with salt and pepper. Grill over medium heat, turning occasionally, until tender and lightly charred, 15–18 minutes. Serve topped with vinaigrette and croutons.