Herding cats.
Herding cats is generally acknowledged to be a futile act. Same goes, it seems, for herding prima-donna programmer/documentation-writer types.
My rule for business-grade projects is the old 80/20 rule: 80% of the effort goes into designing and documenting, 20% into coding. The 'user guides' largely get written before anyone cuts code.
Think like a property-developer: your architect initially produce the spiffy fluffy-edged idealised renders that show the world what the building/bridge is going to look like. Then you get a horde of people to spend time sweating over AutoCAD to produce the plans. Then you recruit East German bricklayers, Chinese roofers, Polish plumbers and Moroccan plasterers to put it all together. And a few Home Counties wide-boys to sell the results.
The open-source community is fundamentally lacking the architects, the AutoCADders and the Home Counties estate-agents. Polish plumbers and Chinese roofers we've got. But we don't let them *plan* shopping-centres.