I mentioned this on SGL as something I would find useful. As it stands at the moment I don't find offsets massively reliable and I believe that better focus is achieved using the filter being used in the imaging run.
To this end, I use 2x bin for focussing, this is fine with broadband filters, 8s per exposure. However when using narrowband 3nm filters I am using 45s exposures to get anything like a decent number of focus stars. I could increase to 3x bin, but if I do tnis I have found that the focus in luminance at 3x is a bit unreliable.
So if I do lum and Ha in the same sequence, I have to keep the same binning for all the filters. It would be great to be able to specify a different binning for different filters.