All points can be used at ANY resort. The only difference between home resort and the others is that you can make ressies 11-months out as opposed to only 7-months for your non-home resort. This is why people recommend buying where you want to stay the most often as you get first choice of reservations.
If you did add-on's at another resort, they would be helpful for ressies there as they would qualify for the 11-month window.
Suppose you had 150 points at OKW and 50 points at BWV's. Your usual stay costs 150 points. You could bank/borrow your BWV points such that every third year you'd have 150 points to use, so stay 2-years at OKW, and the 3rd at BWV, then repeat this. Of course, that 3rd year you would still have your 150 OKW points so you could make an 'extra' vacation, or stay longer, or in a better villa for the next two years.
This is just one example of how it can be done.
P.S, if you're going to make ressies at 7-months, then you can use any of the points any way you want. No need to bank or borrow at all. Of course, in this situation no single home resort has any advantage over any other as far as ressies, so you might want to then just consider the cost of annual dues. (They are different among the different resorts.)