Daniel, a thought:
One approach to this issue might be to create two separate groups of octave lines in the clefs and octave lines panel (similar to how you have already approached clefs).
Availability of these ambiguous house style matched lines could appear something like:
Preferred Octave Lines (dropdown)
Other Octave Lines (dropdown) (or you could take the cheeky approach and go with “Ill-advised Octave Lines”
… another area to encourage correct usage would be an additional category in the Engraving Options, e.g. along the lines of “Preferred Octave Labels” etc.
Another thought — are there plans at some point to open up the lists for the popovers to facilitate custom user edited libraries of clefs and octave lines, techniques etc?
If so, you could perhaps opt to include only the correct and unambiguous versions of these octave lines with Dorico, but if someone had the responsibility to match an existing house style (which is, unfortunately, all to frequently the case), they’d be able to engrave to any specification, needed improvements to the status quo aside.
I want to add that I so greatly appreciate the PAS compliant percussion notation you and your team brought to Sibelius, and at heart, I’m really with you on this attempt at standardization, too, but sadly, while I agree with you here in principal, from a pragmatic standpoint, I thought I should post these thoughts because of the type of work I am often asked to do.