The 18-year-old Morocco international, who impressed at this summer's World Cup, is understood to have already reached a verbal agreement with City over personal terms, salary and contract length, putting the English club ahead of several other major European sides still monitoring the situation.
Talks between Manchester City and Lille are now centred on the transfer fee, with a deal reported to be in the region of €128m plus a further €6m in add-ons - a package that would rank among the most expensive in City's history.
Lille president Olivier Letang has publicly maintained that Bouaddi will not be sold cheaply, saying "few clubs can take on Ayoub's cost right now," though the French club is understood to have identified Real Madrid Castilla midfielder Jorge Cestero as a potential replacement in anticipation of the deal going through.
Should Rodri's expected move to Barcelona be completed, City are also weighing other experienced options to add competition alongside Bouaddi, with Chelsea's Enzo Fernandez among the names under consideration as a more established Premier League alternative.
Rodri, 30, has given his approval for City to discuss a transfer with Barcelona, ending speculation that had earlier centred on a move to Real Madrid before City and Barcelona progressed talks over a deal reported to be in the region of €60m.
Bouaddi's departure would follow City's British-record £116m signing of Elliot Anderson from Nottingham Forest and the imminent arrival of goalkeeper Geronimo Rulli from Marseille, underlining the scale of Manchester City's summer rebuild under new manager Enzo Maresca.
Bouaddi has emerged as one of the most sought-after teenage midfielders in Europe, with Arsenal and Manchester United among the other clubs to have held earlier discussions over a potential deal, though City are understood to be some way ahead of their rivals in negotiations.
One option under discussion between the two clubs is for Bouaddi to complete the move now before being loaned back to Lille for the coming season, allowing him to continue his development in France before officially joining City's first team.