Is there already a digital currency that could accomplish this?
In a weird way, I have to sort of agree with you on this. It has been a struggle to teach most people, including children the 2 decimal places in most of the fiat currencies today. The complexity of 8 decimals are a bit complex for most people.
On the other hand, it seems as though people are more clever than we think, when it comes down to money matters.
Let's take Zimbabwe as a example... On the 15th of June 2015 ... 35 quadrillion Zimbabwean dollars were equal to US $1 {Most people cannot even count to 1 million}
I bought one of these notes for $5 as a novelty item, to remind me, how fiat currency can collapse.
Most people did not do the physical math, they just refered to these notes in colors..or they gave them nicknames {Give me 4 of the blue notes} They also gave sweets & candy as change, because the minting of the coins is too expensive.
In 2008 the monthly inflation rate hit 3.5 million percent with an egg costing 50 billion Zimbabwean dollars.
On 12 June 2015, the Reserve Bank of Zimbabwe said it will begin a process to demonetise the Zimbabwean dollar, to officially value the fiat currency at zero.
In summary, it looks like people could adapt to changes like these, if they are forced to... BUT workarounds would quickly occur to make it easier to understand .
Look at the serial number of that bill, you see the double A? it means that there is huge number of bills in circulation, and the Central Bank ran out of letters (from A-Z) to use, so they add another one.
This sort of thing is happening right now in my country (Venezuela) as we reach hyperinflation. Very, very sad.
With this fact is connected one of the best qualities of bitcoin. Bitcoin is not inflationable because of the exact number of coins which are and will be always in circulation and for the fact that this number is always well known. For this quality can bitcoin be considered as a very strong currency. To tell the right this may cause problems if it will be the only coin of one country but are difficulties that can be overcomes. Even this cannot be sure always because are to many the factors which must and need to be taken in consideration