After additional research, I have a follow up to this original question. I'm now leaning to Answer A, but would like to hear if anyone has other references to support B.
IRC 409A (a)(4)(C)(iii) states the requirement for 12 month prior to date of first scheduled payment is for a payment described under (2)(A)(iv), and IRC409A(a)(2)(A)(iv) is defined as a specified time (or pursuant to a fixed schedule) specified under the plan at the date of the deferral of such compensation.
also
IRC 409A-2(b)(iii) requires any election related to a payment described in 409A-3(a)(4), and 409A-3(a)(4) is "A time or fixed schedule specified under the plan in accordance with paragraph (i)(1) of the section. 409A-3(i)(1) Specified time or fixed schedule states the date must be nondiscretionary.
It seems to me that because the payment is due to the separation from service, which is a discretionary date, then the election to change it must be done 12 months before they separate from service, thus the re-deferral 5 more years is not honored.
The only other thought is that this subsequent change is considered a separate "deferral" and since they are aware of the approximate timing of when it will be paid, then they see it as a fixed/specified date. However, the participant doesn't have the date "scheduled" until the separation actually happens, and that separation is discretionary, thus I don't see how it's permissible.
Curious to see what others think.