One of my arguments with Leavers, Pre Brexit referendum, was that as soon as you put any kind of Border up between NI and The Republic you've torn up up the Good Friday Agreement and the killing will start all over again. I was told I was doom-mongering
Troubles in NI were on the UK news regularly at the time of happening. Since troubles stopped in 1998 (some might say reduced as opposed to stopped) there has been little coverage in media or press. Those that have not lived in NI, or have family connections, will likely have forgotten all about it by now.
As NI is not in UK mainland the Westminster crowd may likely view it as elsewhere and not important? Scotland, Wales and the less well off parts of England are ignored and left out too.
If a border does go up between NI and ROI whoever is prepared to police it should be paid a fortune to cover the risk. Employers should provide large insurance coverage so that any dependents are looked after if the event of anything happens that prevents them from working in the future.