I currently have a BenQ 34" Ultrawide "Designer" monitor. I find the 34" monitors to be in an unfortunate area, size-wise. It only gives me about 7" more width than a 24" monitor.
I'd really like to find something closer to a 49" monitor, which would be closer to having 2 24" monitors.
There don't seem to be any of these that are aimed at designers/photographers, though.
Eizo does not talk about calibration in their literature for this but the few people who have these seem to like them a lot and at a couple grand, the price is very reasonable for what you're getting. The real problem you need to address in your quest is that you are going to need a curved screen to keep viewing angles under control and that can cause issues in how you perceive straight horizontal lines which are not exactly even with your eye height.
Personally, I use two Eizo CG series 27 inch screens side by side but one straight in front and the one angled in, which keeps the viewing angles very close on both of them but it is two separate screens and not one giant one.
The above mentioned Eizo might be the closest thing to what you're looking for even though it's not quite the same as two 24's in one casing.
Unless it is suitably curved, a very wide monitor may exaggerate the visual differences of pixels at centre of screen and side edges of screen. Specifically, the different angle of view may cause colour shifts and/or brightness changes that are not in the image data and would not appear on a print. IPS technology largely overcomes this on "normal" screens but I'd want to check an ultrawide screen in the flesh to be sure it is ok.
You might get some benefit from a relatively "normal" screen shape with higher dpi, but some people (even many, but certainly not me) don't like high dpi. High dpi lets you see more picture within a given physical size.
Personally, I think a taller screen is better because it gives more room for program and OS menus, tool bars, etc. and also handles portrait mode images better. e.g. the old 16:10 is better than 16:9.
