An alternative solution
Given that a a border between Ireland and Northern Ireland will cause significant trade impact to all parties, is the best solution just go with the pretend hard border and wait a few months for Ireland to drop out of the EU?
It's a more workable solution than others proposed and given France are working on a solution involving pre-border checks that will hit all Irish road freight anyway (approx. 40% of trade with the EU and as it is time sensitive, unlikely to be replaced by either sea or air), far faster than government projects... Particularly if the EU decides to clamp down on tax havens...
It's not entirely meant as a troll - if Brexit goes ahead, it hits a significant portion of Irish exports (10% directly to the UK and a further 20% of road freight to other European nations for a total of around 30% of total Irish exports for any tariffs). My calculations maybe a little out...figures are based on EU or Irish statistics.