That phantom reservation method reserving SSR now is possible, but it can only be done if you can do a reservation now that would require 24 OTUPs over and above the total current and banked use year points you currently have to use. If, e.g., you have 76 current use year and banked points in your applicable contract, the suggested Phantom reservation would not be possible because you can only purchase OTUPs that are needed over and above any current and banked points you already have in the same use year. In other words, you would need to be able to do a reservation now that either needs 24 OTUPs over and above the current use year and banked points you have in your account, or alternatively, uses the exact number of OTUPs you will need, if less than 24, when you go to make your the reservation you actually want in Nov.
The other possible downside to doing what is suggested is what happens if you cannot get the actual reservation you want at 7-months out form November time. You will thus have OTUPs that otherwise must be used by end of your use year.
That issue is emphaisized by the time you want, November, a high
DVC demand time at WDW when if it can be difficult, at 7-months out, to get a studio (and often other rooms) anywhere other than at Kidani, SSR, or OKW, and even those can disappear before 7-months out, particularly for the Wine & Dine race weekend (a Thurs to Sun in early November) and Thanksgiving week)
You can, as you suggest, and if available, book 3 of the nights online at 8:00 a.m. at 7-months out from your November start date, and then contact MS at 9:00 to add the fourth via OTUPs. However, that kind of reservation requires availability for whatever you want, both for those first three nights at 8 a.m., and then separately for that fourth night when you want to purchase OTUPs at 9 a.m.