a) There would have been no point in negotiating exit trade deals, as Germany and France especially would have made no realistic effort towards productive talks. As they don’t want the UK to leave (they need others to help pay the bills), it would be entirely in their interest to obstruct these negotiations in every way possible, thereby creating what would appear an exit path fraught with uncertainty.
b) Although 50+% of our exports go to the Eurozone, that is largely because those nations constitute our neighbours, and not implicitly because of the Eurozone itself. In fact, virtually all nations in the world trade mainly with countries in geographical proximity, with some notable particular exceptions such as China, who essentially act as a global manufacturing base.
c) As for the UK “being too small to cut trade deals”, that’s simply not true. The UK is a major global economy, and far smaller nations have cut their own trade deals - Canada being an example in this regard. A/NZ another.
d) Speaking of trade deals, the EU at present has free trade deals with many nations, including the likes of Kosovo, Lebanon, Mexico, and even Palestine - which isn't even a country. On this basis, why would they reject one with a neighbour, which also happens to be the fifth largest economy in the world?
e) Cutting trade altogether, or even introducing nuclear tariff systems, is two steps short of declaring outright war in today’s interconnected world. This is not something done lightly, in fact apart from sanctions introduced vs Russia, post-Crimea, we haven’t seen any examples of this in our part of the world for many years.
f) The EU, as noted above, already feels the pull from the spiralling drain. It wouldn’t take much to tip especially the South back into recession, creating significant systemic risk in the process, and the firepower simply isn’t there to fight yet another looming economic disaster. Were EU members wanting to ‘punish’ the UK for its decision by referendum, they would in effect be playing chicken with their own economies.
g) So in short, it is in everyone’s interest to cooperate. Sure, the EU could hypothetically impose nuclear tariffs, impose significant travel restrictions, and attempt to hurt the UK in any way possible, but the ensuing recoil on their own economies could equally devastate them.
h) Were the EU to ignore all sense and reason and drastically impose the above mentioned sanctions upon the UK in the event of an exit, they in essence confirm their status as a deeply undemocratic organisation which takes more interest in their own institutional survival, than acting on the behalf of their electorate. And I can think of no better reason to want out, because that’s a hallmark of any authoritarian governance.
Finally, yes, there will be a period of instability should we decide to leave. But this election is not about the short term. And in the long run, I personally think the UK will be better off out, especially given the systemic issues plaguing the South of Europe, which will eventually spring back to life.