If I'm understanding you, and if I use somewhat prejudicial wordings
...
In the season when the team flails, they will get to flail for a few extra hours per week after flailing for 45 days.
In the next season (or two), once they learn, they will understand how to do well-enough during the 45 days, and won't require the extra hours.
Furthermore, offering any number of possible methods (that give struggling teams per-season exemptions) to stave off the flailing in the first place sounds like a great thing to focus more attention on, instead of churning ourselves over the unbag time.
If FIRST HQ does implement a weekly unbag period, after a brief transition period, unless struggling teams are simultaneously taught (and willing to learn) project management skills, teams that have eyes/plans bigger then their 45-day abilities now, will very quickly become teams with eyes/plans bigger than 45-days plus Nx8 hours. We will be right back where we started (I predict).
If I didn't also believe that the 45-day building period has value, I would say, "Who cares? Build 365 days per year."; but I think a reasonably-long, limited, build season (a true one, not a fictional one) is a valuable part of the program. I know other reasonable people disagree about that. Thereby hang some tales.
Blake