One of the problems with so many actors in any complex ecosystem is how do they all get paid?
It seems to be a trivial non-technical issue, but believe me, if the participants don’t get paid enough to survive, the very success of any technology will be brought into question. According to the Architecture Reference Framework (ARF), I count at least 10 roles which are critical to the operation of an EUID wallet solution, and all of these will need to be funded somehow - and lets not forget covering any potential liability.
These funds can only be derived from beneficiaries: ie relying parties who provide a service and the user who holds the instance of the wallet. So the money needs to follow the data flows, the question is how is that done, and how is it done without an audit trail which will blow a hole in any privacy expectations?
One answer that comes to mind are anonymous micropayments ("coins") that can be distributed alongside with the data. In a Type 2 wallet, the cost of the transaction should be pre-determined by contract, and the apportioning to each role is pre agreed between each provider, depending on issues like the effort to process, the expected number of failed transactions (which still expend effort) etc etc. It is paid for by the entities that benefit. This can be the User or one or more Relying Parties. The User can add his due as a coin which becomes one component in the data transfer, Payments between Relying Parties to Trust providers could most easily be made by a Payment Provider that could manage the payments without reference to the transaction details, for privacy. Some way of ensuring anonymous payment auditing would be needed, but no doubt could be devised. This could be easy in a Type 2 wallet as the transaction would largely be governed by contract. Payment for attestations and long-life Verifiable Credentials would need to be considered as well. The issue of liabilities, and of proxies etc would also require thinking about at this point.
Type 1 wallet transactions which involve assertions and credentials could be paid for by improved efficiencies at the relying parties. Back-Office payments, like with Type 2 wallets without referencing the User, would also likely be needed. Maybe the User would want to pay for a faster service too.
I think I see a big role for forward-thinking banks here! … and a few more building Blocks in the ARF to support a econmic model should not be forgotten.