The lease pros/cons and alternate MH/toad options have been covered well so i won't rehash those...
But, in your original post, you said "My plan to retire in September, 2018 and live in an RV full-time is being re-evaluated. My plan was that when my auto lease was up in August, 2018 I could lease a big new tow vehicle (maybe an F-350) and buy a 2-3 year old travel trailer.".....
If you had already decided that was the best plan for you, I wouldn't let an unfortunate accident change your plans. Assuming that insurance makes you whole on the existing lease and you owe no money, why not just go ahead and get your new "post retirement" vehicle 7 months early? Its not like its years.
Maybe not an valid option if you currently drive 100 miles a day but if your daily mileage won't exceed your lease restrictions or cause you to spend an exorbitant extra amount in gas, just get the truck now. Its not that big a deal to use a truck as a daily driver. Just a thought.