I didn't read the full long thread below this, but will add a comment at this point.
I am also one of the people who are eager to see ways to channel info into DL, one way or another. And yes, the Android share interface would be nice, too. Although it would raise the same questions/challenges about managing "destinations" and so on - which are also being discussed in relation to the email input interface.
If the email interface is put in place, this can also serve as a "catcher" for Android shares - e.g. via apps like Email Me Pro where you can set up a number of predefined profiles that forward the shared info to a certain email address and with a certain title etc..
Although images/attachments are (probably) not considered for first version of the email interface.
I don't personally have the need to capture a lot of images directly in DL.
If I get that usecase, I will probably set up an easy way to share the images to a cloud folder. Then on the desktop I will drag them into DL if that is where I need them.
(If e-mail input could accept them, I would probably have IFTTT/Zapier email them from the cloud drive).
For URLs I mostly use Pocket for the first, easy capture. They then go onwards to Evernote or my task manager via Zapier/email.
Of course the ability to share directly into DL would be nice.
(If the email input is in place first, I can of course insert it that way).
The most important usecase for me, regarding input to DL, is text notes though. At the very least in plain text. (Formatted/OPML would be good too of course).