I'll bang a drum at this stage - the way thinks are now the FAI need to go with the known product - the solid record and safe pair of hands - Chris Hughton.
Hughton may not light up the world with an Irish team, but they will be solid, disciplined and structured - the players will know what they are supposed to be doing - and with Ferguson upfront, Hughton could well open up the playing style to suit him. At worst Hughton will lay the foundation for his successor (like he did at Newcastle and Brighton).
Have a look at how he approached Brighton's 3-2 win over Man Utd - and having what was no more than a Championship team at his disposal - Ryan, Montoya, Duffy, Dunk, Bong, Knockart, Stephens, Propper, March, Gross and Murray - Man U team was De Gea, Young, Bailly, Lindelof, Shaw, Fred Pereira, Pogba, Mata, Lukaku, Martial.
https://www.youtube.com/watch?v=v_TAQBqKtJk