Its 1980's Ireland, the economy was barely above nuked even without this insanity, but this? Even without the massive scale of damage from this (as you rightly point out the UK is still the dominate trading partner at this point), there's also the fact that Ireland would have just demonstrated its politicians are insane, so bye bye the FDI that was starting to build up at that point with the massive knock ons from that. And then you get into questions like whether the CTA would exist and the impact that would have on the population.
Basically ATL Ireland would be massively poorer, massively more unstable and isolated for decades.