To simplyfy repair mats (to save inventory space) is a good idea, but I don't like reapir mats simply being replaced by those meaningless dark matts, instead, I still prefer fent to repair clothes, leather spetch to repair leatherwear, branch to repair woodstuff, etc. SE, you can just invent some universal fent, spetch ot branch for repairing use, but not those dark matts.
Another thing I don't like is now a crafter has to spend more gils on those damn dark matts to repair their own stuff, rather than making repair mats by their own with very low cost. I do hope those dark matts will be easy to obtain or selling for very low price by NPC.
And goodbye my 1M gils of Spoken Blood which I just bought 2 days earlier...