Macy's is weighing on selling stakes in its flagships. Tishman Speyer Properties will be among those making proposals. TSP has already ventured before with Macy's on Brooklyn store's redevelopment.

 "We will consider any and all ideas for all of our real estate assets in order to create shareholder value and enhance our operations," said a company spokesperson in an e-mailed statement.

According to the New York Post news, to build the tower or two, Macy's - whose flagship in the Big Apple takes up nearly the entire block bounded by Broadway and Seventh Avenue and 34th and 35th Streets - must first get an approval to be rezoned, said the real estate executives. They noted that the store is "overbuilt."

A property that is overbuilt is common for an older city building, explained Richard Baxter, investment broker of JLL, because the zoning text was only written in 1960, long after the site was opened by Macy's in 1902. Over the decades, the store has underwent renovations, and one they began in 2012 was worth $400 million.

City records show that Michael Shah bought the building in a corner of 35th Street and Seventh in mid-2015 for $14 million, as reported by Canmua news.

 Shah said in an e-mail that he would be "open to conversations with whoever redevelops Macy's portion."

 "The maximum for Macy's is about 1.4 million square feet, and it is now 2.1 million feet and about 800,000 square feet overbuilt," said Baxter.

President of the 34th St. Partnership, Dan Biederman, has noted that while Macy's would need some rezoning to "massively increase the size," there are few residents in the area that would be affected.

 "Anything is possible if a developer wanted to take the big risk to take the time and money [to] go through [the city's rezoning process]," said the zoning consultant.