Allow the following items to be used over the weekly cap (just like reputation items).
[Celebratory Pack of Runed Harbinger Crests] (90 LFR Crest → 15 NM Crest)
[Triumphant Satchel of Carved Harbinger Crests] (90 NM Crest → 15 HC Crest)
This will allow for a greater sense of doing lower level activities, while at the same time the large purchase cost relative to the product received will not speed up progress upgrading items very much, which is extremely slow in PvE compared to PvP anyway.