Challenge Modes:How do you intend to balance difficulty without (a) favoring class stacking OR (b) further homogenizing classes or (c) homogenizing the content?
We have seen in the past how every bit of challenging content the players are quite shrewd in discovering which class/role combo brings more to the table.
If the advantage is discernible you'll quite soon get "LF DK tank, shaman healer, 1 hunter, 1 rogue, 1 mage for challenge mode". (and the corresponding and valid complaints of "second choice" and "last choice" classes or roles)
Totally made up example, substitute the class of your liking the only certainty is
there will be a favorable combo if things are done the same way as they've been done sofar and for the exact same reasons.
Storage Space:Any chance we will see specialty profession bags (engineering, enchanting, herbalism, etc) converted to 'boxes'?
Example Blue Ribboned Gift for the type of container I'm talking about.
This would allow players to keep certain categories of items in a box and only occupy a single slot of a normal bag container.
You could control the amount of extra space afforded this way by controlling the size of the box and the amount of 'same kind' boxes you can have at a time (eg. flag them 'unique').
If this is an elegant solution to the limited storage space it could be expanded to other categories than profession bags for example an "armor box".
They would occupy a single bagslot and leave normal bags holding only the immediately usable/useful items and the bagslots being used as temporary bagspace when pulling items out of boxes (but you'd only need to do that to transfer them or use them)