> I was thinking of the case where people want a particular value in
> most of their buffers, in which case they'd want a default, which
> they'd then override for a few cases with a mode-hook. I canʼt judge
> how common that would be though.

I can well imagine people wanting a default for the major/minor ticks, because in most cases that's a matter of preference. But the offset will surely depend on the kind of data in the buffer, don't you think? I think it's unlikely that someone will want all their buffers' lines numbered starting from 10 or something like that. The only clear exception I can think of is someone setting it to -1 to start numbering lines from 0.

Anyway, we can add the customization later if there's interest.