The $1.6 billion Renaissance Center redevelopment plan by two of Detroit’s most prominent companies would include a new Willis Tower-like observation deck — and the project would likely cost taxpayers far less than initially pitched, an official said Thursday.

The GM-Bedrock effort to demolish two towers of the RenCen and open up the riverfront would position the iconic complex for the next 50 years, Jared Fleisher, vice president of government affairs for Dan Gilbert’s Rock, and David Massaron, vice president of infrastructure and corporate citizenship at General Motors Co., said during an event.

The pair used a panel event at the Downtown Detroit Partnership’s annual spring forum to sweeten the pitch for public buy-in of the project, which has drawn criticism and landed with a thud among legislators wary of corporate incentives, including Republican Michigan House Speaker Matt Hall.

When the plan was rolled out in November, GM and Bedrock were asking for $350 million in public subsidies: $100 million from the city’s Downtown Development Authority and $250 million from the state. With no appetite among lawmakers to support the plan with cash grants from Michigan’s controversial Strategic Outreach and Attraction Reserve Fund, the companies turned their focus to the state’s transformational brownfield tax incentives program.

Fleisher told Crain’s after Thursday’s panel that the value of the brownfield tax incentive would likely be $150 million-$175 million, though it’s a complicated equation given the structure of the incentive.

“The ask is for the transformational brownfield program to be extended, and whatever that generates,” Fleisher told Crain’s. “I’m going to tell you right now that it’s not going to generate $250 million … I wouldn’t be surprised if the true value of it might save the taxpayers $75 million to $100 million.”

Developers are promoting that detail in their appeal to the House speaker and other lawmakers.

“So, Matt is already going to win, if you will, for the taxpayers,” Fleisher said. “That’s a great win for him, and we’re going to have to figure it out. But once you cut to the bone, you can’t cut any deeper.”

Fleisher said he hopes lawmakers will support the extension of the transformational brownfield tax capture program because it is performance-based and does not involve funding up front. Rather, it reimburses developers with tax revenue generated from the completed project.

A spokesman for the Michigan House of Representatives told Crain’s that Hall voted in favor of expanding the brownfield program in 2023, but economic development officials have not explained whether it is working.

“And no one has explained why it needs to be expanded again so quickly,” Gideon D’Assandro said in an email. “The point of capping it is so it can be measured and evaluated to see if it’s working. But that’s not happening, so no one can say whether this is a good move for the taxpayers or for the state.”

The tax capture has been tapped to support other Gilbert developments including the Hudson’s Detroit project, where GM will move its headquarters, as well as massive riverfront projects in Grand Rapids.

The Bedrock vice president also teased out a new detail of the planned redevelopment: a new observation deck in the 727-foot center tower that will be open to the public.

“If you’ve ever been to the top of the Freedom Tower or the Sears Tower, now the Willis Tower, the top floor, you have exhibits about the city, you have the (binoculars),” Fleisher told Crain’s after the panel discussion. “It’s something that families love, that people love. Anybody can come up and have the best view of their city.”

Massaron said GM is committed to ensuring the riverfront property becomes a community asset after the automaker’s exit. When the company purchased the 5.5 million-square-foot complex, there was a lot of vacancy and need for large investments, he said.

“We’re continuing to work together on a vision to fix something that we have been trying to fix since the building was first built,” Massaron said.

The redevelopment was also rallied by the other two panelists: Sandy Pierce, a longtime local businesswoman and incoming chair of the Detroit Riverfront Conservancy, and John Waller, principal and managing director at Gensler, the architect working on the RenCen plan.

Waller said a focus of the project is creating a place that retains and attracts talent. The RenCen project would “fill program gaps” by creating a destination along a riverfront that may be rich with recreational activity but has few dining and entertainment options.

“We know that we’re not going to have 10,000 people come back to work at the Renaissance Center,” he said. “We think this is a destination to help fill that gap.”

Pierce, who will succeed Matt Cullen as the Riverfront Conservancy’s chair on Jan. 1, said she supports the RenCen vision but stressed that community must come first.

“What we can’t do when we do this redevelopment, what we can’t lose is local input,” she said. “It’s great for tourists but it’s got to be for the city and the residents of the state of Michigan.”