The biggest problem with covering carbs with insulin is that the carbs are translated directly into fat storage. I don't remember the last type 2 diabetic I met who didn't gain weight on insulin.

The most common sequence is more weight leads to more insulin resistance (higher sugars) leads to more insulin leads to more weight gain. And the beat goes on.

One of the first things to do when a DM2 person goes on a reduced carb diet (less than 50-120 gm/day) is cut the insulin by about 50% or else there are episodes of low sugar, very unpleasant and dangerous. More than having high sugars in the short term.