Friends of the Parks is “prepared to fight for the lakefront” but not ready to say if that will mean mounting a legal challenge to prevent the Bears from building a domed stadium.

Gin Kilgore, acting executive director of the group, tried hard to thread a needle Tuesday, in her first extended interview since the Bears unveiled their $5.9 billion plan to build and finance that stadium and retire existing debt used to renovate Soldier Field and Guaranteed Rate Field, current home of the White Sox.

The group also blocked movie mogul George Lucas from building his interactive museum on Soldier Field’s south parking lot, and the domed stadium could ultimately end up in court. But filing another lawsuit is “not the first thing you want to do,” Kilgore said.

“We are prepared to fight for the lakefront. We are prepared to stand on behalf of the doctrines, the principles that say our lakefront should be forever open, clear and free for public use. … [But] this is not a fully-fleshed-out proposal,” she added.

“There are many, many, many, many reasons to be concerned about this proposal, which is why we’ve been calling for them to slow down the process, involve stakeholders and scrutinize, scrutinize, scrutinize.”

One of her biggest concerns is the three-phase plan for $1.5 billion in stadium infrastructure projects. Only the first $325 million is guaranteed — for road improvements on and around DuSable Lake Shore Drive that are needed to open the new stadium.

Two later phases would be delivered only if state and federal funds are available. That money would pay to demolish much of Soldier Field, converting it to parkland. Without more money, however, Chicago could be stuck with two lakefront stadiums. There also might not be enough money to build any of the bars, restaurants and playing fields Bears President Kevin Warren and Mayor Brandon Johnson, who led the cheers at the plan’s unveiling, have tried to sell as a lush addition to the Burnham Plan.

“It is common in Chicago for promises to be broken — whether willfully or through ‘Oops, we’ve run out of money.’ And there are very few details about what happens in Phase 2 and Phase 3 in addition to the fact that we have no guarantees. And we have examples over and over of where these amenities promised to make a project palatable don’t happen.”

Yet another vexing issue is the Bears’ lease at a new stadium that, like Soldier Field, would be built on lakefront parkland and owned by the Chicago Park District. The Bears want a much better deal than they have at Soldier Field, where their current lease has been an almost constant source of contention over the years.

“They’re asking to keep all of the revenue from other events that might take place at the stadium,” Gov. J.B. Pritzker said recently. “If there’s a Beyonce concert, they want all of that revenue, too, and everything else that might happen there. There are aspects of this that are probably non-starters.”

Under the existing Soldier Field lease, the Bears pay roughly $7 million in annual rent and pocket all game-day revenue from tickets, concessions, merchandise and 4,250 parking spaces. The park district collects on the remainder of nearly 8,000 parking spots.

On non-game days, including concerts, soccer matches and college football games, the talent pays a fee to use the stadium but keeps ticket revenue and the park district gets all food and beverage and parking revenue.

It’s the second-leading source of revenue for the Chicago Park District. Lose that, and “you couldn’t make capital improvements to the parks. You couldn’t operate without raising taxes through the roof. You would devastate the park district,” said a source familiar with the existing lease.

Kilgore raised similar questions.

“What is the impact of taking attention and resources away from the Park District and local parks? … Where are the details? There’s a lot of, ‘Just trust me’ going on,” she said.

Tearing down Soldier Field “in and of itself is highly problematic, in terms of it being a veterans memorial,” Kilgore said. Instead of doing that to create parkland, “why aren’t we investing more money in making sure that more young people can play in their neighborhoods?”

During a sometimes contentious meeting with the Chicago Sun-Times editorial board on the day after unveiling the stadium proposal, Warren said he was not concerned about a protracted legal battle stalling the stadium plans.

“There’s been a stadium on this [lakefront] campus for 100 years,” he said.

Kilgore countered:

“It is disingenuous to say there is nothing new to see here. This is new. It’s a new building. It’s a huge new project. It’s a new location. It’s gonna be a new arrangement. The Public Trust Doctrine is not just about what we have or build on the lakefront. It’s about who it’s for, how it’s used, how it’s accessed. Everything about this is different.”