TM content management option per whole document instead of per segment

When Document A (segments W, X, Y & Z) translated in 2014 has some of its segments (X, Y & Z) reused for document B in 2015, these segments (X, Y & Z) are tagged as 2015. In 2016, segments X, Y & Z are not reused, but segment W is reused (and now tagged as 2016) for document C. In January 2017, you decide to delete segments X, Y & Z (still dated in 2015) because they haven't been used in 2016. But in March, document A from 2014 has been updated and comes back for translation. Because you've deleted what were single instances of segments X, Y & Z, you're only left with segment W to reuse and need to re-translate three quarters of document A from scratch. This could have been avoided by keeping all segments (W, X, Y & Z) linked to Document A in the TM as long as some of the documents segments were reused and deleting segments X, Y & Z connected to document B only.

Paradoxically, by keeping all segments of all documents in the TM and linking them to their own document, this could enable to reduce TM size over time by facilitating segment deletion based on a whole document approach (deleting all segments from whole documents when none of the segments have been reused and keeping all segments of a whole document when a min. user-set % has been reused) without compromising future translations.