I thought you were asking the question, if you've got VFR in your FOM and OPS SPECs then it's not illegal.

If you, as the Capt, feel landing a plane at a non-towered airport without a vis report is beyond your capabilities, then don't do it.

I don't think it's beyond my capabilities, I just think that without declaring an emergency first, it's illegal.

Especially since most non-towered ops are in the midnight-5 timeframe--
having to think a divert might put you beyond duty time limits, limited turn
possibilities, and how do you get an "approved" weather guy out to the field

Having spent 25+ years checking in at sunset and getting to the hotel after sunrise, I've got a pretty good idea of how the ATC system works at night. And I've checked into a hotel a few times at 2am for 8 hours. If I only divert to an airport with WX at 2 or 3 in the morning, I think there will be WX at 10 in the morning (except ILN.)