What would be a better structure?
Depending on your use cases a zip file can work, e.g. Python packages can be imported from within a zip file, and the standard lib is distributed that way.
We have the same issue at $dayjob, the repo is quite large and 80% of it is translation data. Even if they compress ridiculously well (99% last I checked) the number of translation files and the number of exports makes them the vast majority of the cost.
However that structure remains a convenient nuisance, and more importantly removing them would really only be useful if we rewrote the entire repository, which breaks all working copies.
There’s been a task in a wishlist for years now, but the business incentive just isn’t there.
Exit: actually the translation files are 80% of the working copy, they’re closer to 90% of the repo, and on the far side.
Not to mention transgressions often have their own lifecycle e.g. is common to find translatable strings which are untranslated or incorrectly translated, and want to ship updates independently from the software’s.
As such keeping the translations outside the source is also perfectly defensible.
Does this data change as often as the code does? If not then get it out of the repo.