Its actually relatively easy and sorted with 300 euros to the Irish CAA after filling out 2 forms if you are flying for an EU airline with a UK lic. You can even now get a UK national license when you transfer.
I suspect they will not be reasonable and if you are caught in the middle of it all you in for a world of pain.
I say this as a UK national that supports exit. And it won't be the UK that causes the problems.