A marketplace of 66 million comparitvely wealthy people with an economy which by necessity is going to expand is an attractive target for anyone, and a big loss to the EU.
Without the EU we managed to create the industrial revolution , gain an empire which covered 1/3 of the Globe and remained one of the three super powers within my memory. We really need not doubt our ability to function independently.

Now , I address this subject reluctantly because I think all the arguments have been made to a point where it's unlikely that anyone is going to change their minds. Sadly it seems that it cannot be settled by voting since the minority refuse to accept the democratic outcome, and very sadly we know where that leads historically.

As far as your proposition goes, it's rather like discussing the outcome of a football match. We all love to do it and we all have our views, but in the end the outcome will be determined by what happens during the game and our predictions will count for nothing .

Can we , as a nation, go out into the world and compete without German supervision ?

I'm certain that we can, just as you seem certain that we cannot and we won't know till we try. Before that though, we must settle the question of whether the British People , who have voted for Home Rule and independence will be allowed to have their democratically expressed wish, and how much strife there will be before that is permitted.