Without getting into the debate about "will you want a bigger trailer", I'd suggest a 3/4 ton for a couple of reasons:
- it will likely hold some better percentage of it's value on resale (if that's a consideration)
- More capacity to carry additional weight in the bed
- Generally more capable for non-RV towing stuff (other towing, hauling, etc)...if that is of any consideration.
- With the Ford and Chevy brands, I suspect it's easier to get a strong engine/towing combination in a "standard" package on the 3/4 ton than on the 1/2 ton. Even if the numbers otherwise work out, a bigger engine / more towing capacity wouldn't be amiss in the mountains.
My DW is 5'-3" as well: at a little bit north of 60, she much prefers to ride / drive her Sequoia than my F250, but access to the F250 is straightforward with running boards and a grab handle on the door pillar. She does need a step stool for the F550 dump truck....
Our Sequoia is a couple years newer than the OP's Tundra, but (based on towing a variety of things with it, no RV), if the Tundra couldn't tow something, I'd jump straight to a 3/4 ton or SRW 1-ton.
