No way! The rears wear out so fast on those trucks. Don't rotate them. Once you need new rears just buy 1 tire. Use the spare tire as the other. Fronts will last 3x longer than the rears on the Raptor. Why wear them all out?
I'm not sure I follow your logic here. For simple math, let's say the rear tires last a year. Sure, the first time you replace a tire, you'll have to replace just a single. Next time you'll need to replace 2. You'll have replaced 3 tires in 2 years. At 3 years, you'll need to replace the front 2. In 4 years, you'll have replaced 9. In 5, 11 tires. At 6, 15.. The ration will get worse from here since you can't leverage the spare anymore, but you essentially have a rate of 2.5 tires per year over the first 6 years.
If you regularly rotate the tires so all 5 tires rotate evenly, a single tire will spend 2/5 year in the front, 2/5 in the rear, and 1/5 as a spare. If 100% wear occurs for rear tires in the rear, than a single tire will be 23% wear from front use, 40% wear from rear use, and 0% from spare use, or 63% wear. That means you'd need to replace all 5 tires at 1.67 years..or 2.99 tires per year.
So it does look like you'll save money with your method (although savings get worse, except you can often get a free tire when you buy 3 or more, so the rotating method is actually pay for 2.4 tires per year. And, if you have any uneven wear, that can be more easily worked out when you rotate the tires.
I'm not saying your plan is wrong, just that it's certainly not a clear winner.