These are impact assessments Brydo ‘ worst case scenarios’, painting a picture of doom and disaster, and that is why the Remainers wanted them published , and why the remain media have heavily latched on to them!
It does not mean that they are fact , just possibilities – they could happen of course, but probably in a trickle rather than a flood!
In any good business the board will have impact assessments available to cover all eventualities, it is common practice, and I say that as a retired board member.
The EU as a group, and the individual member states will have exactly the same ‘worst case scenario ‘ assessments as us- we are not unique in this, but political expediency is rife amongst the opponents of Brexit.
The most important word in the whole of your post my friend is ‘could’!