The Irish economy is mainly beholden to the UK in terms of exports. Scotland made a case for independence based on the price of oil - it dropped by 50% in recent years , they would be bankrupt by now or destitute. Wales spends more than it gets in terms of GDP growth. I dont know about N Ireland - but I guess it wouldnt be able to keep it's standard of living - without cutting spending or raising taxes.
This is where stupid nationalism gets you it seems - worse off - but hey at least you'd be independent? , unless you dont count Brussels. Wales would be getting handouts, have to abide by all EU laws and standards regardless, and no matter who you voted for - it would make a difference. (you could argue we that with Westminister now)
People in the North think like you, people in Cornwall think like you and people in South East could argue they'd happily kick everyone out unless they lived within the M25.
Which is why (IMO) be better off (given your scenario) with England and Wales - than some sort of pseudo EU member - none of the benefits and all of the restrictions.
I really have to concentrate on my work from here on in.