I'd like to see a new tick box included called Full Length Documentary.,  Because, as well as it is nice to have the 'little featurette box'  there.. Most featurettes are just that ..  A Short Movie ... 'three to 20 odd minutes.''  .

But a Full length documentary such as the new Cinerama Adventure
included on the the new HTWWW set is over 96 minutes in length and is by itself a Movie or a nights entertainment on its merit. and even the 1980 Movie of the Stunt Man Limited Editon has a 114 minutes of a special called The Sinister Saga making of .. really got into everything.. Point is.. A lot of these special featurettes are in fact a Documentary. I'm sure there are countless others.. 
But I vote for a need radio button or tick box called Full Length Documentary.   

Seconded.

Very good question.

Maybe it would be better to add a runtime field for featurettes.  And when there are like 4 featurettes with 15 minutes each, runtimes will be added to show: Featurettes (60 Min.)

EDIT:

Another approach could be to differ between featurettes and documentaries.
Maybe by saying a featurette with a real cast & crew credit role is a documentary. 

But for me runtimes would do, as you can see if there are only a few minutes or some hours worth of featurettes/documentaries.

Quoting Snark:

Quote:
I am not sure that would be the same though... There's a difference (IMO) between a full length documentary then 10 ten minute featurettes...

Could get a bit tricky for example with the load of featurettes on i.e. the "Alien Quadrilogy" release:

Each film has on Disc 2 a 2-3 hour documentary, but it is splitted into 10-30 minute segments with unique titles, each separately selectable from the menu. But only after the last segment is a credit role for all of this parts.

While I like the idea to differ between 10-minutes-merchandising-everybody's-great-featurettes and feature-lenght documentaries, I can see making a clear rule is going to be a really difficult case.