Hi Anita
cheers on your 70.3! I’m in a similar boat, some thoughts
As you said, you probably want to add some buffer weeks to your FD plan (vacation/sickness), so start maybe 2-3 earlier
Also over such a long Phase of training it may be beneficial to have some time off from structured training, but that depends on your mental and physical needs (training burnout prevention).
So depending on how you decide you can go with SSB or Traditional Base before your FD plan.
It’s a good time of the year to get strength training going, which you later maintain.
I did little intensity on running last year during the post season, max 30-40 min at easy, but often. Helped me to be fresh for the next phase. It took some mental effort to not continue on all the tempo runs and intensity but I had a great season afterwards.
Finally check out this thread Long term plan for a 70.3 A race next August