Yes, you can use tags for segmenting large works into smaller chunks.
And it is possible to use them for other things as well. Besides segmenting the work, I use them for MIDI vs PDF, as well as Score vs Parts (vs Lead Sheet), and sometimes for instrument-specific differences (in instrumental doubled or transposed parts), all at the same time.
This is something I practice. I have a script that will create the necessary files for the project that will compile a score and parts that can be built into a blank project. It relies on some templates, plus a list of instruments. It works fine enough that I haven't had to look for another solution.
Like any of the solutions discussed on the list, this is not a one-size-fits-all bullet and requires wrangling with some decisions about how you want to structure your content. You will likely have to deconstruct some of what you already have to work in any templating system. It is also somewhat of an iterative process, since you need to start with a template of the global definitions and timings, before setting up the template used to generate the instrument-specific files of musical content.
In any case, your pain is felt. But it is possible. I generally do scores of 9-12 staves at 200-400 measures and it took me quite some time to arrive at a solution that works.
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