As states open insurance marketplaces amid uncertainty about whether they are a solution for health care, Vermont is eyeing a bigger goal, one that more fully embraces a government-funded model. The state has a planned 2017 launch of the nation’s first universal health care system, a sort of modified Medicare-for-all that has long been a dream for many liberals. The plan is especially ambitious in the current atmosphere surrounding health care in the United States. Republicans in Congress balk at the federal health overhaul years after it was signed into law. States are still negotiating their terms for implementing it. And some major employers have begun to drastically limit their offerings of employee health insurance, raising questions about the future of the industry altogether.