If you rear-end someone and they decide to go after you for more $$ than the insurance payout, you could be in trouble for pulling more weight than the vehicle was designed to safely pull...and stop. There are plenty of ambulance chasers out there that will look for any angle to separate you from your $$ and this negligence would be all they need. Either way it's ultimately your choice. Just seems to me that the cost of tow package is negligible compared to the worst case scenario otherwise.
They can go after you for more regardless. Parents are / were attorneys that handled car wrecks. They can gladly try to get more than what ins offers no matter what. In my state, it will come down to a Jury deciding on what you get. The fact that you were towing 2000 lbs when you were rated for 1500 may come up, but the fact is you are still at fault. Its also pretty pointless to try to get more than what your Ins covers, as most people dont have alot of assets, and certain things like Primary Homes and retirement are protected from litigation.
I think what the Original idea of this post is why the different ratings, so lets look at what the towing package is, and how it helps
1. Bigger Alternator - I guess this would help with a larger trailer, as some trailers can be charged by the tow vehicle using a 7 prong plug. No affect on towing ability.
2. Larger radiator - Now i could see how this could assist in towing more weight, but not add to safety of towing more weight. From diagrams, it appears the coolant may be used to cool the trans fluid. Keeping temps down is important to the life of the car, but not safety. Also, multiple forum members have towed loads w/o the towing package and not seen a huge increase in engine temps
3. Trans cooler? - this is still up in the air if there is a difference in cooler between towing and not towing package vehicles.
4. Anti Sway - OK, if this is real, and i think its really just the built in stability software, it could help with sway, but sway is usually caused by an improperly balanced trailer to begin with. Most sway is caused by not enough tongue weight. Cross winds on a large profile trailer can cause it too. However since the OP is looking at a popup, this is not a huge factor.
So with that said, i don't see much that really added to the safety of towing a larger amount of weight. Now, i think a towing package would be beneficial if it had any of the following
1. Larger brakes - this would be nice for slowing down larger trailer down long grades
2. Lower final drive
3. Tow . haul mode from trans, or even a way to control gear selection
4. Stiffer rear springs
5. Built in trailer brake controller
Now if the package included anything like this, then i would agree that the package really makes it safer and more practical to tow a larger load. But, since it does not, it really is just a way to sell a 1000$ package, that if more common, many of us would buy. However, they are rare, and in the case of my L, not even available.