Re: "The potential downside of not getting this right is very serious,"
First, clearly not a disaster, in fact not even an issue. Translating data from one format to the other is not new nor rocket science
Second, it is clear we have little to no influence at the moment, at least once we are out we can decide not to store and share banking info with the USA (for example) if we wanted (I suspect our weakling governments will still fall over themselves to lick uncle Sams...)
Third, I have never understood why you remain people think that voting to continue to make a massive payment to lose control over trade relations, energy policy, tax policy, purchasing policy, ability to support industries we consider vital, important or strategic while at the same time also suffering a massive trade imbalance with the group is actually somehow the brainy thing to do.
This last one I equate to a simple analogy...
I pay my next door neighbour a fee (£10 a month). This allows me to sell my car washing service to him for £10 a month. He sells me his grass cutting and window cleaning services for £15 a month. This allows me to sit idle most days.
Meanwhile the fee I pay him:
allows him to setup all the car washing, washing up, grass cutting and window cleaning deals in the country
allows him to create a rule that requires me to take the lowest price for everything
and what is left of the fee is then used to subsidise his other neighbours children so they can do the washing up cheaper than my children.
All in all it seems to me that I would do far better to cut my grass and clean my windows, pay my children to wash up and tell him to stick his fee where the sun doesn't shine. Still, I guess it must be nice to know others think the original story is the most beneficial version and clearly gives me great control over the dividing up of washing up in my street and not agreeing makes me a total idiot.