Placeholder order is the check I would add next, because it is the one that turns into a crash rather than into a bad string. A translator reordering arguments is perfectly legal when the placeholders are named or indexed, and it breaks the call when they are bare positional ones like %s, since the runtime takes those in sequence. So a reorder should be an error for bare positional placeholders and a non issue for the indexed kind, which means the tool has to know which family a file uses.
On unchanged strings, expect false positives from proper nouns, OK, numbers and short UI labels that really are identical in both locales. A per key ignore list, or a minimum length before that rule fires, is what keeps the finding useful instead of noisy enough to be ignored.