I see it more of a question of limiting reactants. If your limiting reactant is resources than stop build day is disadvantageous, because you aren't working on the second robot. So it helps well-established teams, but it appears less well-funded teams like it. And I personally like it. And a longer build season would not help and only stretch the gap between teams.
I Have two suggestions:
Increase the out-of-bag time to 12 hours. Out-of-bag time is not like normal build time because there is so much extra time to get things and is more even than just letting the second robot builders practice.
Let drivers practice as long as no mechanical changes are made this would include fixing it. If this decreases the value of a second robot your closing the gap between teams. Unforeseen consequences aside.
Keep the stop build day.
Side note: My feeling about the Un-even stop build time was that on average it helped with the gap. Given that on average east coast has more money than west. Also I loved ending at midnight.