+1 to everything that polyglot has said.

My own view is that you have to get rid of all haze, fungus, finger smudges etc that might cause a reduction in contrast. Even if the scene isn't high-contrast, it will just take the edge off every image you make if it is there. If you want to take hazy pics of models, then you can apply vaseline to a filter which can be easily removed afterwards. Lens hoods help a great deal if the issue is direct light striking the front lens element. But it will help nothing if the issue is internal flare or ghosting, especially when the sun is behind the camera. I should add, I own a lot of Mamiya MF gear, but no TLR (apart from a Yashica D). So my comment is generic, not related to your particular lens. I'd be very, very surprised if the TLR lenses are so badly coated that the issue is the coating rather than something on the elements. But as polyglot has said, 12 stops DR is stretching it, even for a state of the art lens and film combination. If the highest and lowest values are adjacent in the image, then you can expect difficulty to some degree. And if you insist on photographing every difficult scene what that same camera despite knowing better, then you obviously have to live with the consequences.