I would like to see an inventory system so I can see all of the items I have on stand-by. This would help plan for which heroes to bring up and if you are running low on something prior to finding out when you go to upgrade.
I think it would be awesome if you could post an item you need to Alliance chat so that way if you have a player that has a surplus of an item you need they can donate to the cause to make your alliance stronger. I am not saying it would be a limitless donation (ask for one and possibly receive 35), but set limits on it so that you can receive little bonuses.
Green - 10 donations
Bronze - 7 donations
Silver - 5 donations
Gold - 3 Donations
Platinum - 1 Donation
(This is the total possible to receive per request, not per donating person)
An Alliance Store would be cool too, you get points for running raids with alliance members, and donating items, or even have them as a bulk reward from events for alliance placement/contribution. You can even make tiers of the store so as your alliance levels up more items become available.