Jack,
TD is right about the practical concerns. Even without a bunker, I would build a mound with the diversion swale above it. You never want to take care of uphill drainage close to the green. Sometimes, routing the cart path to the high side allows it to act as the drainage swale.
As to the original ?, I have always preferred them above the green, for visibility. Since so few golfers hit over the green, they are usually mostly cosmetic. That said, I recall playing my Cowboys GC with Notah Begay III, who went nuts at the idea of a downhill lie to a green falling away, saying it was a really hard shot he didn't care for in his designs.
Which brings me to your last point, it is as close to a cardinal rule as you can get - greens ought to tip to the downhill side, which sets up the situation above. Greens that drain back into the hill always look awkwardly perched. Even greens with minimal cross slope (assuming the hill is more on the side than back) can look perched. I often reserve my biggest cross slope (maybe 2.25%) for such greens.