Good questions to ask.
Unfortunately i don't have any answers.
Soviet Union, via planned economy, had an autonomous currency (that couldn't be forex traded (or even leave the country)). Its value was stable. Don't know if this is at all relevant - probably not - just thinking aloud.
How could we acquire BTC if it can't be traded ? Could it be allocated according to (a pre ordained/consenually agreed upon) contribution to the network (economy in the case of the Soviet Union). Maidsafecoin (safecoin) will work in this manner, as I understand it - coin allocated according to drive space/bandwidth/cpu time etc. Of course, these things still have to be bought.
How about contributions that can't be bought ? I'm thinking of intellectual contributions being rewarded with coin. The value of the contribution would be consensually arrived at/agreed upon by each and every other participant of the network. Evolutionary, kind of.
Again, just thinking aloud - I'm sure this stuff has already been discussed elsewhere (many times)
But yes, when you are relying on it to buy a loaf of bread - or pay your mortgage - a 20% drop in value within 2 weeks is not an acceptable characteristic of a currency.