Thanks for all the valuable info you posted above.
Allow me a remark on one thing, though:
With only the slightest sliver of reservation it can be said that digital currencies are already legal tender in Europe even if they're not sovereign money.
Your "slight sliver of reservation" looks like "strong doubt" on my side: "legal tender" usually refers to "anything which when offered in payment extinguishes the debt.".
This is not the case for bitcoin. It's also not the case for gold bars or houses or our beloved Auroracoin.
The german bundesbank offers another definition:
Legal tender is the means of payment that nobody can refuse to settle a monetary obligation without experiencing legal disadvantages.
For the case of germany they state some legal fact:
In Germany, banknotes denominated in euro are the sole unrestricted legal tender.
Not even coins are legal tender in germany without restriction. The obligation to accept them is limited.
Surely one can refuse to accept cryptocurrency for settlement of debt. Otherwise I could pay my taxes in potcoin, which would be outrageous, no?