As it just came to me:
What if we implemented a selection when the user creates a new document
so they can actually choose what fits their needs best? (Possibly with a
checkbox "remember as default")
Pop up a window and ask "What content do you want to create?"
- "digital art (pixel based)"
- "content for print (mm based)"
(I imagine a big button for each with one showing a computer display /
smartphone and the other showing a piece of paper).
Option one would create a pixel based document with a useful size (e.g.
800 x 600 px²).
Option two would create a scaled document (e.g. A4) with mm units (i.e.
the current default template)
Maybe we could even add a dropdown to the latter where the user can
select (mm, meter, inch, ... or even px)-based so most bases should be
covered. (An inch-based default template could even further be
specialized to be letter-sized)
I think that might solve a lot of confusion and frustration around the
whole "default" template as one default might just not be enough...