IIRC, you have the KAF-16803? I don't think you can really use that as a gauge of the performance of the ASI1600.....
It is possible to use a shorter scope with a smaller sensor to achieve the same FoV, though....
I am not using 16803's performance to judge ASI1600. I am using my experience on 16803 to understand the limitation of the LRGB composition with mono sensors. My science training makes me very careful on what experience can be transported to different situations and what can't. For example, a big disadvantage of 16803 (and all other Kodak CCDs) is its high read noise. I hate it a lot, and I criticize CCDs about this all the time. However, I know that ASI1600 has much lower readout noise. So I will never criticize the ASI one regarding its readout noise and any issues associated with readout noise (such as sub lengths).
As for using a short focal length to get FoV, you loss resolution at the same time. If one wants to maintain resolution (with proper sampling of the stellar FWHM) and get large FoV, simple math tells you that the right way to go is high pixel counts, not short focal length. Of course, the real word is much more complicated. We can adjust focal length and pixel size to achieve Nyquist sampling, but there are always limits. We are forced to live with limited choices of focal lengths (if we do not want to change the main mirror) and limited choices of sensor size/pixel size combinations. So it's never simple, but the basic idea of going to high pixel count is still valid.