Nah I think we have plenty of inventory space, especially when you consider 2 retainers and housing furniture/storage in the future.
If you have excess dyes just sell them on the MW and buy more when you need them.
I do agree with the tackle box for fishing though, but this should be a quested item.
The main problem I see with this line of thinking is, if we have separate inventory for dyes what's next separate bags for materia, potions ? food?
That being said, if people really want more space maybe ask for a quest line to increase your inventory, such as the gobby bag quest in FFXI.
