I'd have gone with McMillan but if we have an option of a player like Hoban returning, fit and in form then he can do the same sort of job. O'Donnell would be the toughest to replace, a player that can dictate tempo, does the simple things very well, retains possession most of the time, links back to front, can protect the back 4 and pop up with a goal. He is a big game player too - there are not too many of those around any league.
McEleney still is the big potential, if fit and consistant in form, he is the difference in unlocking teams that pack defence, I love the sort of player that has that something special like a Matt Le Tissier or a McCourt and McEleney has that kind of flair so Id go with McEleney on that alone. But really its an impossible question!! lol Like we missed Benson early season and like Finn you only really see what they give to the team when they are not in it. It will be an exciting prospect to have out and out wingers with the full-backs overlapping at pace next season and freeing up space in the centre for him to strut his stuff as opposition defences are overloaded.
Sheilds is the cult hero type like Gino that we all love in our side but would love to hate if he wasnt, but not completely irreplacable, he is a pretty classic no nonsense League of Ireland player.