I think there's scaling issues to consider, and, for a change, good ones rather than bad ones. A small currency with only a few tens of thousands of dollars of US$ equivalence in it can afford to be purely ethereal. A little less secure, too (though not egregiously poorly secured, which is the usual case for a new system of any kind).
After all, in the end, money is simply confidence. I don't believe in the gold standard because I believe it fundamentally misunderstands the nature of money (and of gold, but that's another story). Money simply is the confidence that the next person will also accept it, and the fact that the confidence chain can be broken is not fixable, it is fundamental to the nature of money. US Dollars, even gold-backed, can have the same problem, and note that the reason we're talking about this at all boils down to fear that the US dollar won't be as useful as it was before, that the US dollar won't be good enough to keep the local economy going.
A smaller system, especially if it is truly geographically local, can engender confidence in ways that the larger system can not; "I know everybody using this", or if you prefer, more ominously, "I know and have easy access to where everybody using this lives".
You can grow this like you could grow any other enterprise, I think; the system you get out of the gate that works in Small Town doesn't need to be the same one that works in New York. The only tricky thing is that I have no idea how to monetize this; who will want to buy a currency that you're taking a profit from? And it will need to be monetized; there's some risk here that I wouldn't touch with a ten-foot pole without an LLC minimum, and that LLC sure wouldn't take it on for free.