The post-production house believes that as TV departments at agencies shrink, multi-tasking among creatives is becoming critical.
Ogilvy & Mather and Lowe are two of the agencies testing the scheme, preferring not to send people off-site whenever possible.
"The main advantage for us is geographical. It's a much better use of creatives' and producers' time," Charles Crisp, the head of television at Lowe, said.
Pat Joseph, the managing director of The Mill, said: "This is financially beneficial to agencies that would prefer to use on-site resources for less complex projects or for international versions of commercials."