I don't know why we couldn't have one. Lots of other MMOs have done a mats bag, and with the set up they have in XIV a craft bag would only make more sense. I think it would be fine if the craft bag was accessible from your inn room/apartment/private quarters, as long as you could craft from it while in the room, makign it more of a craft repository than a craft bag... You'd still have to carry the materials back there to drop them off, but there should be an overall lightening of the load (so to speak) even with that system. Also could have the added effect of clearing up some of the clustering of players around summoning bells in the market areas.
Crafting has always been a bit of a sticking point for me and a few people I know...typically boring, if not boring then time consuming at least, and it usually proves to be difficult to keep it up with your combat class levels to keep them relevant. Particularly if you need stuff from killing mobs like Leatherworking does in XIV. Unfortunately I haven't any ideas on how they could fix that...aside from maybe adding in a greater level of automation. Being able to tell your retainers what mats to go after would help a little maybe...