I am one who thinks old habits can change which means any camera can become like an old glove if one gives it a chance. Most often cameras with "bad" ergonomics, are just ones for which new habits have not been adopted yet. I easily go from D90 to D7000 to D800, and the few times I have had longer uses of the D3s. I think that comes from not expecting other cameras with different design goals and periods of development to be just like whatever I got most used to. Whatever you get, in a week you will think it is the best ever unless you focus on how different it is than your habits every time you pick it up. If you tend to do that to yourself, my sincere suggestion is to not buy anything new. You have a camera which can do all you need now. Any fairly modern DSLR can. We are at point that it is hard to tell the difference in output between the lowest level cameras and highest, so if one is resistant to change they are in luck because there is little need to change any if the old habits are too near and dear. A D3200 is capable of taking any photo hanging on any gallery wall.
I was more interested in your take on adjusting things often for creative reasons between shots. My suggestion here is that you are limiting creative options by not concentrating on good solid data capture and great composition, such as properly exposed and focused which means getting a focusing screen for use of your MF lenses and leaving AWB activated, optimize exposure for best capture of minimum lost data and not worry of about creative expression in-camera. With digital, it's just bits, the creative manipulation occurs in post processing. You have a world of creative tools and opportunities in post, that if tried in-camera, would result in lower data quality. Good exposure assures the best raw material to work with. Good composition and good exposure are the photographer's contribution to in-camera quality images. Lighting and composition trump all else, so your camera related field tasks are mostly related to those instead of intentionally compromising camera settings for less than optimum data capture for artistic reasons. In the field, get the capture, use the tools that work really well such as AWB and now, AutoISO. Get the capture, take it home where you have a calibrated large monitor and do your creative work there when you can see what you actually have. If it is not print ready, it is easy to change in post to anything you want. Same with focus, get the focus, if you need it to be less than sharply focused, you can blur in post but you can't fix an image that is not in focus at capture. A D600 has the added advantage of not having to adjust ISO so often. Set the aperture for DOF, SS for the speed of the subject and let Auto ISO work within the range you set as the highest acceptable level. The incredible DR of these new cameras really helps simplify your field tasks.