How will it stop smuggling?
Smuggling happens Worldwide and is unstoppable for as long as the same goods have different values depending on where they come from.
How does it stop the fact that on one side of the boarder people have benefits that those on the other side do not even thought they voted to remain?
There will never be a; policy, law, legislation, regulation that pleases everyone on the planet. There will always be winners and losers.
And how long do you think these things take to set up? Ready for Oct? I'm going to go out on a limb and guess you also think we have "the tech"
Not ready by Oct 2019 that's for certain. The Port extension in Mauritius took 3 years to build, but one year of that was due to the Project being wrecked by a Cyclone. Two years would have been enough without the cyclone. Mauritius has a population similar size to NI.
I know leavers live in unicorn land but honestly
I did not vote either way. Your comment is yet another example of those who support remain looking for obstacles in the hope that Brexit will either be thwarted or a failure so they can say:
Na Na Na Na Na we told you so.
Odd logic as the success or failure of Brexit will affect everyone regardless of how they voted.