The idea — a theme park in South Miami-Dade — is not new. But Miami-Dade County hopes the second time’s the charm.

The county is reviving a stalled plan to develop oodles of vacant land it owns around Zoo Miami, and its goal is hardly modest: No less than a South Miami-Dade version of the Universal Studios theme park, with maybe some Downtown Disney thrown in for good measure. Call it Ricky Mouse.

The county parks department has issued an invitation to bid to developers: basically, an open-ended plea for bright ideas, conceptual schemes and — this is key — private financing.

The invitation is now under the so-called cone of silence, designed to bar lobbying during bid consideration, so county officials say they can’t identify potential developers. But they say some serious players are interested in helping the county fulfill its longstanding vision of turning the zoo area into a major tourism destination and an economic generator for perennially struggling South Miami-Dade.

“It will bring people into the area, and they will spend money, and that means jobs and economic development,” said County Commissioner Dennis Moss, whose district includes a large swath of South Miami-Dade and who has long pushed for a theme park at the zoo property. “We feel the timing is right, and that at the end of the day we will have a credible proposal.”

This marks the county’s second pass at securing a development proposal for its properties, which besides the roughly 120 acres being made available under the invitation also include the zoo, the adjacent, lesser-known, Gold Coast Railroad Museum, a long-in-the-works military museum, and about 140 acres of protected pinelands that cannot be touched.

After years of groundwork, including rezonings and a 2002 master plan, the county in 2009 issued a request for proposals for a water park, hotel and family entertainment center on vacant land by the zoo, running along both sides of the main entrance road from Southwest 152nd Street.

But it drew only two responses, neither of which officials deemed feasible. They blamed the recession and the county site plan and specifications, which consultants subsequently told them were “too restrictive,” parks director Jack Kardys said.

This time, parks officials say, they drew up a request designed for flexibility. It designates the land available and broadly describes the county’s goal of a themed, water-oriented resort and entertainment destination integrated with the zoo and the rail and military museums, but leaves the specific components and layout up to the applicants. The county can then pick the proposal it likes most, or none at all, Kardys said.

“We’re asking developers what they think would fit here best,” he said. “These guys do this for a living.”

Proposals are due by April 30, after which they will go to an evaluation team that will make a recommendation to county Mayor Carlos Gimenez. The evaluation would probably take about three months, Kardys said.

During a planning phase that preceded the issuance of the bid invitation, Kardys said, interested developers floated ideas ranging from movie studios to a Main Street USA theme and a themed water attraction and hotel.

“It’s been pretty interesting,” he said. “I think we’ll see something that gets themed in that Disney, Universal Studio type of thing. That’s the kind of ambience and thematic development we’d like to see.”