I can't see what the problem is here
Photos app contains all the photos you take from all the devices in one convenient sub section of the photos app, ironically called photos. Neatly split into collections by date and place.
You have your shared albums available too as a separate sub section.
As usual all photos sync and download to your mac photo app of choice when you turn it on and open the app.
I don't understand the logic behind deleting photos but wanting to keep them somewhere else, like the cloud? I've read people want to free up space? Aren't you guys managing your photos. Endless streams of photos gets a bit boring. People should be moving their fav pics into albums and you can share these. get them into your computers photo app, sort and rate them and you will have them in albums allowing you to clean up your photos if you need to delete some.
There is no longer a part duplicated set of photos called photo stream. This seems logical to me. I don't have to worry what size photo I'm seeing, the original always downloads to the mac.
And to address the 3rd party import issue, I'm also a enthusiastic photographer and often I import large files from a d610 or fairly big files from a x100s, in both cases I don't want these in the cloud. I specifically turn off upload to photostream on import. I don't need to see massive quantities of burst shots and rubbish shots.
As with anything my photos for iOS are neatly organised into the photos section from all devices, my 3rd party stuff organised into folders in my Mac photos app and I pick my favs and publish to a shared album which allows me to group and have that album available on all devices. I can also share that with others if I wish and they can now collaborate and add their own photos too, ios and device dependant.
iCloud drive I agree on, it is slightly confusing. There should definitely be an app showing what you have stored there, just like google drive and drop box. I think this is a natural evolution. I still don't understand why photos aren't available via a web browser but that's a feature request