Bitcoin/Bit/Satoshi is the way to go. Each range of 4 decimal places will cover 10,000 units, which is easy to remember, and the names are easy to say. And look at this beautiful little thing below. You can express this whole naming scheme in two lines!
1 Bitcoin = 10,000 Bits
1 Bit = 10,000 Satoshis
Simplicity. Marketability. Roll-off-the-tongue-ness.
I like this, but the amounts wouldn't make sense to people in terms of most transactions, buying a coffee would cost 100 bits ?
Well, shit why not? Certainly at least 100 units of value can be extrapolated from a cup of coffee, right? maybe 10 units for the cup, 10 units for the water, 50 units for energy consumption, 30 units for service.
It's considered a small purchase, so it's kind of a clusterfrack for most people to call it 100 of a currency, therefore we need something like 'bitdollars' or 'bitpennies' that represent 100 of them.
Then again if we ever reach the point where people regularly buy coffee with bitcoin around the world, maybe 10 bits will really be what it takes to buy a coffee.