A Boston company's request for an exclusive, 60-day window to fashion a bid to buy Jackson Health System appears to be dead, politically and legally. Several members of the Public Health Trust, which oversees Jackson, said Monday at their monthly meeting that the offer from Steward Health Care System that came last week is intriguing and should be explored, but not on an exclusive basis. Joe Martinez, chairman of the Miami-Dade County Commission and a member of the Trust, said it is "totally, totally premature" to enter into any agreement with Steward. Later in the meeting, he also said a deal to sell the county's hospital system to a for-profit company such as Steward should be considered only as a "very, very, very last resort," adding that such a deal also probably should be approved by voters. Eugene Shy, an assistant county attorney who handles Jackson, said the law does not allow one entity to look at Jackson's records without letting others do so as well.