That's a damn good question.
Several of us have done it... but I really do not think the healthcare.gov people are consistent in how they deal with applicants. IMO, you're getting someone that's inexperienced and just working a job moving papers around. This seems to work for the cookie cutter applicants, but not so much for the things that fall out of the norm (like us.)
I went round and round with them and finally gave up. AFTER I gave up, I got "congrats you're approved". AFTER getting approved, I still get once a month mails saying they need more data. (It shows approved on healthcare.gov and I'm still getting subsidies, so I'm just being silent.)
I feel like every time you upload documentation to healthcare.gov you create a new thread... and different people are working on the different threads. They ask for more data... you give it to them... new caseworker on new thread while old case worker works the original thread with new documentation.
Bottom line: there really seems to be no rhyme or reason to it. I decided to give them everything they wanted, including last years taxes which mean nothing for next year. I also gave them a letter from my employer stating I voluntarily retired and about 3 different letters from myself breaking down how I was funding my retirement on a month-by-month withdrawal schedule. I gave them summary pages of the accounts I would withdraw from and previous dividends.
I then just decided "screw them... if they reject me, I'll pay the full price and get a refund in 2017." Don't fret too much over it. You can't predict them.