A universal default.svg with units px and scale=1 provides a simple single solution to a number of issues:
- Resolves broken extensions and features like symbols and outset/inset, etc.
- No need for users to consider scale, they just set the display units and work.
- No need to tailor localizations with in/96, mm/3.77953.
- Fewer bug reports for scale and localization issues.
- Neophytes are less likely to abandon Inkscape as confusing or complicated.
That's a lot of benefit, for what could be relatively little effort.
Like with any graphics or CAD application, users should be familiar with setting document units when starting to work. This is the most basic of best-practices.
Even making a template is not difficult, but a button/tool to save the current document as a template would be very handy.