Ok, thinking a bit more about it I guess you’re right. If we want a painless update, the next version should be 1.0.2.
What is more, I now think the approach taken by the CSL 1.0 Specification Update 2010-05-30 that I’ve already quoted above is right (although the distinction between minor and major incompatibilities is not quite clear.)
So, the new in-text feature should be on 1.0.3. (It is backwards compatible.)
The next additional backwards compatible feature is 1.0.4. etc.
choose would perhaps be a good candidate for a 1.1. release. It’s backwards incompatible, but it’s perhaps still a minor incompatibility.
Changing the datamodel from flat to hierarchical may be considered a major incompatibility, so that would be 2.0.
Does that look feasible?