But that's pretty easy to do. I made an FC with only 1 other player by just giving a /shout asking for a couple others to join us momentarily just long enough to get the petitions. If doing it by yourself, you'd need 3 other people rather than 2, and at least 1 of them would have to stick around a few minutes to invite each of your alts as you switch out between them, but that shouldn't be too much harder. I know a number of players have done it that way.
Well, ranking up is a lot slower to do alone, but you'll get there eventually. (I've done most of that ranking up alone since the friend I made the FC with didn't stick around long. I've reached rank 6 so far, but it took a long time.) In the meantime, you do get the first tab (50 slots) of the FC chest as soon as the FC is created. That's not a lot in the way of direct storage, but you'd be able to pass items around between your alts if you want your alts to store stuff for you, or if you're going to be playing all your alts and want to pass stuff to them. (For instance, I've only leveled crafting on one character, but use him to make gear for my alts as well.)
It's definitely a lot more convenient, though, to have extra retainers for storage rather than a storage alt, since the later would require a lot of logging out and back in again just to shuffle items around. Plus you can't directly check what's in your alt's inventory. (I do this in another game I play, but that game allows add-ons so I use an add-on for keeping track of which character has what items in stock. With no add-on support, that's not possible here.) And retainers can hold bound or untradeable items, while neither the FC chest nor an alt can.
Those are the reasons (even with a personal FC and a few alt characters) I store nearly everything with my retainers. (I have passed some festival items —sparklers and the like— to one of my alts to hold, and I had an alt hold all the assorted gardening seeds I gathered until I was able to get a house and garden. But I keep all my crafting mats with my main character so that "Search for Item" will work, and I keep all my extra or glamour gear with the character who earned it since so much of it is bound anyway.)