Most importantly, what are you going to use your truck for? The weight/size of your tires is not really relative to whether your stock suspension can handle it. It's unsprung weight. The stock suspension (shocks, springs, TB's and AHC components) won't be stressed from the added weight of tires. Bumpers would be completely different. You're looking at close to $4k for bumpers. That's a lot of $ and WILL have an affect on the amount of sprung weight your stock suspension is carrying. Most would consider it a negative effect. It's going to add a lot of weight to your truck.
I'm not familiar with AHC, which your new truck probably has. But, your front would probably hold the weight of an ARB bumper (without a winch) just fine. Although, you need to do some small cutting to add the ARB, it doesn't just bolt on. The rear would probably sag pretty good under the added weight of a steel bumper. Especially if you add the swing out tire carrier. It wouldn't feel as smooth as it does right now, and might even bottom out.
If you're concerned with an extended warranty, I wouldn't do anything except just drive it the way it is. I'm guessing you won't be going offroad much, so why not just enjoy owning one of the greatest vehicles ever made? Although, you'd be surprised how well these truck perform completely stock. If offroading is your goal, then I might reconsider either the year/cost or the extended warranty. If you want to do all the mods, cancel the EW and use that $ to add mods that will benefit your use.
Not to make this a tire thread, but as far as tires go, remember your truck will have 18inch wheels, not 16's. A 275/70/18 will fit stock with no issues. Some other sizes will fit too if you keep your AHC set on "high". Everything you do will change the way your truck feels and drives. It might be worth it to drive a modded 100 and your new 100 to get an idea of what you're willing to sacrifice. For just plain driving down the highway, or the occasional dirt road, I would leave it just the way it is. Running boards and all. It will never be smoother than it is right now.