So what apertures will you typically use when you stitch?
I use whatever the targeted image requires, just like for non stitched images. I am not sure why the use of stitching has to impact the choice of working aperture?
Overall my baseline is f5.6, but I use the whole range that provides good image quality, again depending on the image I want to achieve. Currently, I tend to avoid shooting more open than f2.8 because the images quality degrades a bit too much for my taste at f2.0 on the Zeiss 50mm f2.0.
We do not know yet how much better the 55mm f1.4 will be at f5.6 but that will only be one factor affecting my decision. Having a near perfect f2.0 would be very valuable for me to shorten exposure times in distant panos at dawn/dusk. Alternatively, it would enable me to drop the ISO 1 or 2 stops without impact on image quality. Light fall off will also have to be confirmed.
Other key factors will be the level of chromatic aberations on edges and in oof areas, the quality of bokeh, the overall rendering style,...
The lens is obviously the key element in terms of look, what else matters?
I respect your choice to select your equipment based on the convenience factor, but my criteria remains the best possible image quality. That's why I used to use 4x5, that's why I owned a MFDB and that's why I stitch with a D800 now with some of the best lenses available today. The day when I feel that convenience is more important will probably be the day when I will know that I need to change hobby. But that is just my approach to photography and I respect others.
It does of course not mean that I will carry my D800 with a Zeiss 55mm f1.4 all the time. There are of course times when a smaller/lighter camera is the preferred option. I also use the Sony RX100, Sigma DP2m and Nikon V2 + 32mm f1.2 depending on needs. As a side comment, the Nikkor 32mm f1.2 is way too expensive, but is a pretty amazing lens.