Lessons have been learned from the Troubles and the Good Friday Agreement and these can be taken to help ensure peace in a United Ireland.
The Troubles started because of inequality between Protestants and Catholics under a Protestant Northern Irish parliament which denied many Catholics - and working-class Protestants - basic human rights such as housing. This does not have to be the case. If a framework can be devised which includes protections to ensure all groups are fairly represented and their human rights are protected, a united Ireland can be a peaceful nation.
Violence against civilians and profiling from security forces was also a key reason for the escalation of the Troubles. Again, lessons can be learned from this and a softer, cross-community approach such as that of the PNSI can be followed to police Northern Ireland rather than the tactics of the Royal Ulster Constabulary.
The Good Friday Agreement and prior agreements also provided a framework for peace. One key feature of the Good Friday Agreement was a power-sharing government and a 'decision-making by consensus' approach. This can be applied in a united Ireland to ensure unionists feel democratically represented. In the same way that all-Ireland institutions were set up as part of the peace process, British/Irish institutions could be set up in a United Ireland.