Paddy Lowe has admitted Williams could start using Mercedes' gearbox and rear suspension in 2019.
It comes as the rise of 'super teams' with satellite outfits becomes ever more commonplace in Formula 1.
Ferrari has Haas and Sauber, Red Bull and Honda have Toro Rosso, Renault is tipped to move closer to McLaren, and now Mercedes could expand its relationship with Force India and Williams.
"It's an option we don't want to dismiss. Given the changes that are happening in F1, we must keep an eye on all the ways of operating a team in order to maximise performance," Lowe, the technical boss at Williams, told France's Auto Hebdo.
It is believed the rise of 'super teams' is the reason Renault is opposed to Mercedes' involvement in the resurrection of financially embattled Force India.
"We have nothing against Force India. But this topic must finally be on the agenda. We have been talking for months and no one is listening. This is our chance to publicise it," boss Cyril Abiteboul told Auto Motor und Sport.
As for speculation McLaren could be a Renault 'B team', Abiteboul insisted: "McLaren will continue to build its own cars and will not become a B team."
But even the FIA is worried.
"F1 could soon be dominated by two or three super teams," admitted Charlie Whiting.
