Constructive criticism. I'm a bit skeptical of the idea for 3 reasons.
Voters aren't all that interested in the election yet. Yes, there is some interest, but even the record audience for the first GOP debate only had around 10-15% of America tuned in. A sizable percentage of Americans are not even familiar with Sanders and if they don't wish to spend 5 minutes reading about his platform, why will they watch a 1-2 hour long documentary? The most likely viewers will be hardcore supporters, and Bernie already has them locked up.
The cost of the documentary. How much of that money could be spent on ground operations in states like Iowa which have proven success rates? Obviously, if a supporter decided to create a documentary in their own time and the campaign endorsed it, that would be a win-win, with no drawbacks. But if it has to come out of campaign funds, I'd like to see that money put elsewhere.
Why Netflix? YouTube has a much larger reach and doesn't require a subscription. A documentary like this would need to go viral, and that would be difficult if it's behind a paywall.
If a documentary was to be made, here's some ideas:
-I'd like to see it released later in the campaign cycle, perhaps on television much like the Obama campaign did in 08. Of course, Sanders can't get to the general unless he wins the primaries. Perhaps a documentary that is aired on cable television? My worry again though is the cost of airing the documentary versus the cost of simply running 30 second advertisements.
Either way, to generate a new supporter, they have to be open to new information. If they are open to new information, it'd be best to start by sharing his platform, TV interviews, etc. If a voter is still undecided, then maybe a documentary would do the trick. But I just wonder how many people would really fall into that situation, especially since many people are persuaded due to his platform and ideas without the help of a documentary.