I have just been producing a major documentary for universal in the US and then directed an independent one in Africa. Couldn't agree more, in fact the very well know cinematographers on both (who incidentally shoot big hollywood films as well) reminded me that if you want to make good drama you have to be able to make great factual. Look at Paul Greengrass and Christopher Nolan, both started their lives working for BBC factual. Besides which I haven't seen or made a documentary yet that wasn't crafted and scripted by the creative team. The only difference is your 'stars' are being paid to perform in drama so you expect them to deliver, where as with documentary you are pleasantly surprised when they do.