In my opinion, the key would be to insure the deposits in a nominal amount of fiat. For example, the insuring entity (whether a company or the government) will insure deposits of BTC up to 70 USD/BTC. This number would have to be revisable periodically to keep it below the actual value of Bitcoin, but it would serve to give people a safer place to put their bitcoins to keep up with inflation via interest. It would also solve a lot of issues with capitalizing projects via bitcoin (buh-bye BTCJam).
Alas, this is only my wet dream. It's unlikely to happen in an acceptably regulated fashion.
I think I'll write a blog on this tonight. Share your ideas to help me.
I do this now, but with silver instead of dollars. You can get no less than 4 oz silver bitcoin specie for each bitcoin (and currently a good bit more than that). The QR code on the pieces creates a flexible market based bimetallic standard (gold standard / silver standard - but only silver is released so far), with a floor value of the nominal value (1 ozt silver / quarter bitcoin).
I would never be so bold as to guarantee a level of fiat currency against bitcoin (I'm not the central bank), but I certainly would with a commodity monetary form. It is looking like the 2014 one ounce silver will be a bit-dime if things move forward as they appear to be which would put the floor value of bitcoin at 10 ounces silver .999 fine for the bitcoin specie.