In a way this might be similar to not crossing the dateline during Sefira. The Rebbe made his opinion clear that IF the dateline is crossed, Sefira is for the individual and שבועות should be celebrated (בצנעה) based on personal count. It is obviously preferred (by the Rebbe) to totally AVOID crossing the dateline during Sefira.
So too in the case of לישב בסוכה for הבדלה. It is definitely preferred to have a קביעות that is מחייבת בברכת לישב בסוכה לכל הדעות, but in case that isn't possible (or in a different Sukkah?) one should make a לישב בסוכה when making הבדלה on wine even with no other קביעות.