I don't normally enter into Murabitun discussions because I don't really know much about their group. But I have a couple of things to say here:
1- Paper Money is not Haram, although it is sub-optimal.
2- Since many people seem to have a desire to bring back gold and silver currency, what is stopping us?
I mean, why do we need the entire Ummah to agree on something before we do it. Why can't the Muslims in a given town just decide to trade amongst themselves in silver coins? Why couldn't they then go to the local stores and arrange for the stores to accept them as well?
In my hometown, the Jews have their own paper money which is accepted in most of the stores in their whole section of town. If they can do it, we can do it.