Not sure they can offer that much
They are in the customs union but have a subset of the single market (free movement of goods only). If the UK leaves the SM and CU then they do too.
They then face the same third country problems that the UK does. Data adequacy will be the least of their problems. Given that the Isle of Man will be behind Cornwall and Scotland in the queue for food supplies in the upcoming Brexit zombie apocalypse, their best hope is becoming part of Ireland.