Republic of Ireland star McGeady played under O'Neill at Parkhead and the Villa boss is keen to organise a reunion this summer.
New Hoops gaffer Neil Lennon knows Heskey well from their days together at Leicester and wants him to be part of his Parkhead revolution.
The former Liverpool striker fell behind John Carew and Gabriel Agbonlahor in the Villa Park pecking order last season and would jump at the chance of regular first-team action north of the border.
O'Neill reportedly wants to add out-of-favour Tottenham striker Robbie Keane to his playing pool and is also keeping a close eye on Stephen Ireland's situation at Eastlands, claims the News of the World.
Manchester City are believed to be close to wrapping a £25million deal for Villa star James Milner, and O'Neill will use the funds from that sale and Fulham's capture of Sidwell to add the new faces he wants to his squad.
Sidwell is desperate to return to London after two years in the Midlands and will seal his move to Craven Cottage before the start of the season.