Storage rooms only have a singular purpose and are a highly neglected room, both in strategy and functionality. Most players wont upgrade them until end game, and other then allowing more inventory space, add very little to gameplay.

My suggestion is to allow dwellers working the room to produce 1 bottled of purified water, and 1 food item. Although, this comes with the cost of increased food and water consumption when the storage room is being worked. Storing food while un-occupied by dwellers can lead to food lose due to rats that seems to occupy the vacancy or even more increaded rad roach infestations.

Now, why produce bottled water and preserved food when propperly maintianed and operated production rooms supply more then enough for your dwellers? As any wastelander you welcome into your vault will tell you, some good water and food can be worth more then a plasma rifle or a handfull of caps. Maybe even the rare wastelander will trade for his copy of nicola tesla to help your dwellers better maintain their vault.

Esencially, I am sugesting explorers be allowed to carry water and food like stimpacks and radaway, but to have a chance to trade water or food for caps commonly, weapons, gear, or even the chance for something more rare. Letting your explorers of the wasteland carry around these extra items could also slow down thier expiditions if endurance is an issue, or possibly open the ways for raiders or other shady people to approach the explorer depending on how special they are.

Although this idea might help in the midgame it would have no impact on the end game ... food and water are the least of my worries and most of my explorers are already staying out long enough to come back with full or nearly full inventories (and my caps are at the max 999,999 so getting more is not beneficial) ... I would like to see a fourth level upgrade on storage (more space) until they can add a sell all non-rare or sell all in a stack option for inventory management

You assign dwellers to the storage room? Interesting.

I don't see why a storage room should produce something... Nothing gets produce in any storage room in real world, except for rats, molds...

But that dwellers should guard it, that, I agree with. So each storage room should have at least 1 dweller, otherwise the room could cost food loss (for example).

I typically, will assign a dweller to a storage room when their highest SPECIAL is Endurance and I either have no room in a Nuka-Cola bottling room or don't have a bottling room. It keeps them happy since the storage rooms are E rooms.

If you are careful, you can do the same thing with your dwellers whose highest SPECIAL is Charisma and the Living Quarters. By careful I mean you should use two separate Living Quarters.