They didn't allow for map stacking because they don't want people to horde maps.
What amazed the heck outta me is stackables are now 999. Although personally, I'd prefer seeing mats in a dedicated tab, like we do for crystals. Hell I'd even be willing to give up a page or two in my pack just to have this. Maybe one page per expansion? Even if it was just 99 per item. (trick would be to have both NQ and HQ mats, although I suspect if they ever did this, HQ mats would not be able to be stored.)
All things considered, they're doing a lot to aliviate the storage issue.
It just cost us a DRK and MSQ roulette to do so.