Hi Peter,
Here are a few comments on your essay:
Don't ignore SNR. It is all that really matters. Image integration is all about SNR and it doesn't make sense to think about it as something different.
Yes, exposure time is the key element. More exposure time collects more photons and more photons means higher SNR (signal increases faster than noise.)
Setting sub time based on FOV makes no sense. Do you mean the scope aperture? That would make more sense but is still an oversimplification. You need to consider focal length and pixel size as well.
Your suggestion of integrating stacks of short and long exposures is close to a useful technique for dealing with very wide dynamic range in an image except that you need to combine the two stacks using HDR techniques, eg. the HDRComposition process in PixInsight. Combining them with image integration won't do anything useful.
If you're interested in developing an understanding of the basics have a look at the articles on Signal to Noise by Craig Stark:
http://www.stark-labs.com/craig/articles/articles.html
Another really good source is the Handbook of Astronomical Image Processing by Berry and Burnell.
Cheers,
Rick.