In fact, smart businesses will new open offices in UK (outside of EU), just to hedge their bets on the future. Buy low, sell high.
Being in the EFTA would mean continuing to obey EU legislation, continued freedom of movement and paying money into the pot, ie. everything the Brexit campaign was against.
So, no, those agreements will likely not remain in place. The EU wil not agree to give the UK all the benefits of EU membership without the costs.
There may be other benefits to Brexit, but it will not be the case that Brexit will be good because the UK will negotiate a deal that, of itself, is better than the current deal the UK gets.
Not everything. For some people it was about symbolic sovereignty, or even about the legal structure.
Those are pretty big "ifs," don't you think?
You appear to be reading different newspapers than I do. They are all reporting "forget it" to these options.
Where power originates with people, manipulating the general opinion is the ultimate source of power. Ever heard of "bank runs"? It's like a self-fulfilling prophecy -- once you manage to scare enough people, you can shape reality. Healthy banks fall. Threads like "Should I leave the UK because of Brexit?" pop up.
What I'm saying is there is (as in, must necessarily be) very little implications of "Brexit", technically speaking. What will really happen is all about what people's emotions make it to be, which are in turn shaped by whose PR prevails.
How (what mechanism) is this a necessity?
Bureaucracies are not productive enough to enact changes like Brexit in a short amount of time.
Europe will need to determine exactly the ruleset which they believe will apply to UK imports/exports, and it will be extremely costly and slow to make any significant changes, since whatever is decided will need to flow down to multiple agencies.
Consider, for example, the cost of rewriting lots of technology to support a new arrangement for the UK. Can it be done in 2 years, 4 years, 6 years in every single country that the UK trades with?
It will be easier to have arrangements to continue with what we have for now and then to grandfather in what already exists at some point.
(This is just my layman's perspective and it's based entirely on intuition so I could be completely wrong!)
On the contrary, it is necessary for the EU as a political project that there are negative implications of Brexit, and that those negative implications are perceived by everyone.
But isn't that what membership of the EU gives the UK today? So give up the membership, you give those up to. It's kind of the whole point of the EU.
Scary how people equate those, without understanding the (monstrous) difference.
All the things you list have either been already implemented in the EU, or their implementation is being actively discussed.
The gradual loss of sovereignty (the so-called "salami method") is also what prompted many people to vote for Brexit. Not everyone was a knuckle-dragging racist.