A few more considerations.
Name of the Country
What do we call the new state? Ireland? United Ireland? Obviously we can't use anything Irish 'cos it will offend the Unionists.
Flags
It's been mentioned already but flags. We all know how contentious they can be.
National Anthem
It would be a big sacrifice but I'd give up the dirge that is Amhrán na bhFiann in the interests of peace and reconciliation. Danny Boy anyone?
Currency
Since the ROI is in the EU, I guess the new state would have to stick with the euro.
Taoiseach
As an Irish word, it wouldn't go down well with the Unionists. Do we replace it with the title Prime Minister?
President
Do we stick with Michael D. Higgins or hold an All-Ireland presidential election to elect a new president for the new state? It would have to be someone with a link to the two states. Dana anyone? Oh wait........
Car registration plates
Do we stick with the ROI reg. plates - year and county? What's the UK system of numbering? Random numbers and letters?
Passports
The citizens of NI would have to surrender their UK passports. I know some citizens already hold ROI passports. In the interests of fairness, do we scrap the ROI passports and issue everyone with new All Ireland passports? How long will this take and will the new passports be ready in time for the summer holidays?
Income Tax
Who currently pays the highest amount of tax? I suspect it's those of us in the ROI. In which case, I vote we go with whichever system deducts the least amount of income tax.
Stamps
We'd need new stamps.
New Bank Holiday
To commemorate this very significant event (the reunification of our two states), I propose that we create a new Bank Holiday. In November. 'Cos we don't have a Bank Holiday in November and it's a cold, dreary month.
Anything else I'm missing?