Does anyone think it would be a good idea to come up with say.. 10 things that we just HAVE to have (I personally don't need that many), and perhaps 5 things we would like to have, and maybe another 5 we don't want to see?
What I think would be most useful to to come up a list of must have functions for the top tasks photographers need to do that Lightroom can't, here's mine...
Retouching...how it's accomplished, I'm less concerned with how it's done and more concerned and how easy and efficiently it would be done. Will that require Photoshop tools? I don't know, but if you need to make selections to do accurate retouching of areas, then a lot of the features will be almost self evident. Clone/heal/content aware/blur/smooth/control texture and replace elements which leads to compositing.
Compositing...yes, we need to swap out heads/faces, skies, add photo elements together to combine them. Does this need layers? Actually, I'm not at all sure. Yes, if you think in Photoshop terms, but maybe not if a new compositing engine could be developed.
Yes, to HDR, Photomerge and focus bracketing...must haves. And there are third party developers who have made really nice small scale apps to be able to accomplish these tasks far better than Photoshop.
Image detailing. LR's capture sharpening and noise reduction is very good (I helped create it). Lightroom's output sharpening is very good (I helped create it) but "creative sharpening" is still very primitive in Lightroom. And for one really good reason–all Lightroom processing must be done parametrically. To do substantial and radical creative sharpening needs to be able to get access to pixels and return rendered pixels. Photoshop CC's Shake Reduction is an example...it's pretty cool and does a good job determining the required point spread function and applying an optimal deconvolution kernel sharping. Could this be done in raw? Maybe, but it already works with pixels. LR's -Sharpness does a pretty good lens blur of limited radius and strength but doing stiff beyond that is tough to do parametrically. So, capture and output sharpening is pretty good now, it's the creative stage that is currently weak in LR.
Yes, 8, 16, 32 bit functionality a given...yes channels and masks a given. For precision, paths for making selection as well as color/tone ranged selections ala Color Range (but on steroids) because Auto Mask is ok but limited...ideally this sort of masking should be available both parametrically and also for pixel based selections and adjustments.
So, the point here to to encourage thinking about what we need to do, not to get wrapped up in how to do it.