I like this idea as well, but start out as an individual player market the progress to an alliance market. Keep this as a trade market not a donation. This way players can only trade their goods for other goods, for example, surplus gold can be traded for need food to upgrade troops or barracks and vice versus for surplus food to gold.
Even though we'd all like this it's a bad idea. To give you an example some new player could join our alliance and we could literally spoon feed him resources to level everything, since a lot of use have extra resources that go unused. This would literally spare him the trouble we all went through to get where we are. I'm fine with trading trade goods which are harder to get and can't be used for upgrades. As for gold and food however, it should be up to every player to work for what he'll get.