Is there any information missing on an individual transition basis, or is
it more global matters (links, start/end points, range of transitions) that
is missing information?
I don't recall exactly the formats you're using, but the thing I most remember is not being able to handle all the data. zdump should be able to dump everything, not just transitions for a limited number of years.
At some point, perhaps far in the future, there should be a pattern and zdump should be able to deduce it and output it and stop. zic already does this sort of thing.