I’ll try and find the thread but there’s many people that do exactly that, split the plan and insert a recovery week in the middle. I wouldn’t personally FTP test in between since you’re just inserting a bit of recovery into what still is a base plan.
Check these for reference:
I’m curious about a couple things though:
“a lot of z2” - maybe have a look back at previous base periods where you did burn out and were the extra rides all actually lower intensity, or were they maybe higher intensity and even with the low volume plan it was too much without a break? Perhaps you could adjust the additional rides. Speaking from personal experience here of over extending myself many times.
I’m not sure of the answer of this offhand since I don’t have a LV plan to reference but plans were updated with some knowledge gained from AI - you might compare the current LV plan with that of previous years to see how the workouts may have changed in the plan and how that might impact your training/recovery.