I hesitate to answer this question, because you're basically asking me to put down what I think is acceptable level of renting, which is hard to answer as shown by DVC's unwillingness to do so. I can put forth what I think would be accepted by most everyone, and state that I'm not opposed to it, even if I don't fully agree with it. Without devoting too much of my precious and limited mental capacity to solving DVC's problem for them, I would say something akin to a percentage averaged out over 3 years in addition a hard cap on points. Don't hold me to the numbers, but something like if you rent out over 33.4% of your points averaged over 3 use years, capped at 1000 points total for those 3 use years. So if I have 3 contracts totaling 1000 points, I can rent all of them 1 year, and nothing the next 2, 333 points each year, or any combination therein. That allows you to rent out an entire year of points if a crisis comes up.
"Lots of people"? I don't agree, as evidenced by availability. I'm also not talking about using stray points or last minute reservation, I'm saying not a single sane person is going to take their 11 month home resort BWV BW view studio week long reservation and trade into SSR at 7 months. You can find one offs like the person above who wanted to trade into a treehouse villa for the extra room, but that isn't what I'm talking about.
How do you determine break even? You can rent Poly straight up for 21/point as a point rental, and upwards of 30/point if you spec rent. At even 21/point, with dues of what, under $9 a point, that's 12/point extra. Even after taxes, that's still a large chunk per point. Are you taking into account buy in? That would be unusual for such a comparison.