Tbh Den,a USE scenario is the only one which can actually work. Providing they can convince the peoples of the nations involved to accept it without squealing too loudly.The current system of one currency with many different financial regimes / systems attached to it cannot ever work under any circumstances,as I think has been proven in recent times.
I have no doubt that the powers that be fully intend for this to be the final outcome,but they cant admit to it of course.It has to be a case of slowly slowly catchy monkey.
This latest expensive sticking plaster will buy them more time to work out the best strategy to proceed in that direction.It actually creates a big opportunity to move faster, if they play their cards right imo. 
Yes, I've said that before son - the EU makes no sense without total integration – all foreign, domestic, financial policy, a common system for administration of justice and so on.
Naturally that’s why it won’t work in the way envisaged – each nation is too disparate, the values and aspirations held by the peoples of each nation comprising the membership is sufficiently different to render an amalgam of common purpose impossible.
The common association of trading nations - working to make free trade - was certainly a laudable enough goal, but the monster that was spawned when certain people saw the opportunity to weld the differing nations into one super state knocked that original intent into a cocked hat.
It is a dangerous desire to have ‘Brussels’ as the sole voice of Europe’s mass choir and, soon after total integration, the song being sung will less than tuneful to the many ears within the new state.