Concept. Some discussion with Paul Grignon, the author of Money as Debt.
Digital Coin proposal: 
Just a hint: change the chart to show "value of CC" in function of time, not the reciprocal. That is how people think about money (and yield as value grows with time).
Denomination note
As we start to deploy the system, the only way I see is to use a common denomination devised from some currency basket (deviating +few percent a year).
The basket and percentage can be decided by the monetary committee. Initially in Hungary we propose basket containing EUR only, but +3% / year compared
to EUR.
In USA and Canada a basket of (USD, CAD, EUR, CHF, JPY) might be more appropriate - as a start.
When the system scales and grows large, bankers' fiat currencies devalue fast as the money velocity increases.
But than as awareness grows, it's easy to make the next step to use basket of goods not basket of currencies for denomination.
The reason to split into consecutive steps
1) create money outside the banking system (still using fiat currency basket for denomination)
2) make a proper denomination
is not technical, but psychological. It's too hard for people to understand both at the same time in the beginning.
The proper way to do 1) create money outside the banking system
is by auditable and interconnected LETS systems, not a central PC-issuing authority.
This provides robustness against central failures, corruption or attacks (legal or other). And, perhaps first of all, LETS systems are something that people can understand.
Summary:
A) we advertise a denomination system. Originally linked to a fiat currency basket, later slowly changed to basket of real goods. Or abruptly if we can reach a hyperinflation of USD and EUR (that would be a quick - although not the most fair - way to get rid of the fraudulent bank-created debt). This denomination is used when someone wants to maintain debt in more than one complementary currency (own issued Digital Coin "CC" or LETS)
B) I, a personal entity register at the network of our notaries
C) I declare in digitally signed document that my maximum debt in CC ( Digital Coin issued by myself) is ..., LETS-1 is ..., in LETS-2 is ..., in printed paper cheques is ..., debt toward the banking system is ..., private debt through unauditable systems is ..., all this in function of time. Denomination is according to A). Only this declaration can glue the currency systems together without the whole becoming a giant mesh of fraud (again). Effectively everyone can decide which systems he uses, but the systems enforce he cannot go into too much total debt.
D) each publicly auditable system enforces this without publishing actual balance or transactions
E) LETS systems (or other complementary currency group) do the clearing among them with the help of a ripple-like network.
This provides high flexibility and robustness without much risks. The only risks are again: psychological. The key to win is to clearly, understandably distinguish publicly auditable systems from trojan horses (intentionally made by the bankers, or other corrupt parties) that will be used in massive media campaigns to turn people AWAY from ANYTHING SIMILAR. Do not underestimate the mass-manipulation capability of bankers
F) The developers should rely on small fees that grow significant when the system gets deployed worldwide.
- In my vision Digital Coin CC is mostly for companies.
- While LETS is mostly for private persons. Companies (or any fictive or anonymous entity) can join a LETS but never go negative. Only private persons can go negative.
Each LETS and CC issuer or complementary currency group can deviate, but risk that market does not value their currency (can still be useful internally) and there will be a huge warning flag attached.
Psychology (marketing). Technology: censorship-resistant sharing.
We need both Digital Coin CC and the LETS network. Consider that people can understand LETS but not yet prepared for Digital Coin CC.
This will change of course. But always consider the psychological factor. This game is 30% technology and 60% psychology. (the remaining 10% is mostly "legal" blabla).
Out of the 30% technology maybe third or half is monetary tech (issuance, auditing and clearing). The remaining is cypher-communication: censorship-resistant sharing.
Not solved yet.
