What do you think you would do, sell (which doesn't really hurt DVC), make the most of it or add on more points?
Well, it would depend on what exactly they did. For example...
1) If they kept my dues the same, but offered discounts on dues to those with lots of points. I would have no problem with that.
2) If they gave members with lots of points a 2 week booking priority window at the resorts (e.g. 11 months plus 2 weeks & 7 months plus 2 weeks). This would depend entirely on what it did to availability. If I saw that I was no longer able to book my choice of rooms (within reason) at 11 months out at my home resort, then I would be forced to sell.
3) If they charged a fee for banking/borrowing. If it was a small fee I would not sell. However, DVC certainly bills the "fabulousness" of being able to bank/borrow points heavily when you join. So if the fee was excessive, that would make me strongly consider selling, as I typically bank a few points left over from our joining bonus each year.
4) If they offered
DCL, ABD, etc. discounts to high point holders. Since those discounts would be extra perks, this wouldn't bother me at all.
So essentially what it boils down to for me is whether anything they did was an added perk for large point owners or was an added fee or dis-incentive to smaller point owners. I have no issue with large point owners getting discounts, reduced fees, in-room gifts, etc. I would have a big issue with large point owners getting benefits that directly impact my ability to use my own points such as altering my booking window or charging me to bank/borrow my own points that I paid for.
While eventually I'd like to do an add on (I can easily see us wanting a 2 bedroom once we have kiddos), I wouldn't do it just to get in a higher tier if I couldn't afford it already, which I can't right now.