From a commercial perspective it's a league with a combined population of around 30 million, which would make it the eighth largest in Europe. It wouldn't be as attractive as the others as they all operate in one economic area with one main language, this league would have 5 different economic areas, 3 in the EU, 2 outside, 5 different currencies and at a push 3 languages if we group the Swedish and Danish together. In four of these countries English football teams are the best supported club sides. Football isn't even the most popular sport in Ireland and none of their clubs attract any kind of significant support.
It has the potential to be a stronger league than the SPFL financially and certainly it would be more competitive, but it'll still be miles behind the big 3 or 4 in Europe. It's not an easy sell.