This could be an interesting feature, e.g. if you want to translate the same source text with different translations.
Imagine you have different types of length restrictions. So you could set custom length restrictions (e.g. max chars per line, max lines per paragraph) as structure information inside the paragraph, and set a penalty if the length restriction of the already existing translation is different. In this way, it could be avoided that the shortest translation (which might be so abbreviated that it's hardly readable) is stored and then always used for translation where the translator could use a lot more characters.