The European Union is not an organization for inter-governmental cooperation between friends and neighbours.
The fundamental purpose of the European Union is, and always was, to supplant and eventually destroy European nation states; and to impose an undemocratic, unaccountable system of technocratic government, which can never be removed, so as to lock in that purpose.
Whatever one’s political philosophy, be under no illusions: a vote to Remain is a vote in favour of that objective. All the rest is trivial.