Maybe I'd have to see it to understand, but no matter how Sonar were set-up, adding a bar before bar 15, for example, is always going to push out all the other bars.  Even if the piece were built in sections, added bars in the early sections would push out bars in the later sections.
 
Maybe what you are requesting is to have measure (bar) numbers that start over with 1 at the beginning of each section.  I don't know a way to do that and most people who work in orchestras or bands would find that confusing when the director says, "bar 32."