Thank you for the thoughtful post.
Presets are not for everyone, but you would be surprised at how many photographers rely on them for a good starting point or to create a look. That is also true for Auto Enhance and their ilk.
Selective adjustments are a frequently requested feature for the app. I have implemented a prototype of such a system, though I am so far behind with 3.0 development, that completing this feature will have to wait until after 3.0. If you look on Twitter for @gentcoders you will see some older tweets which show that prototype implementation running in a test application. You may find that of interest.
Film grain: yes, I would like to add a film grain adjustment to the app – I don’t think it’s very difficult. However, I was unaware that the grain should be applied differently to highlights and shadow areas. Can you tell me more? You mentioned a ‘hill’ – is the grain function applied most to the midtones and then less to both highlights and shadow areas?
Thank you again. Happy New Year.