A coalition of Massachusetts unions who represent state and municipal workers have added their own health care proposal to several others. The proposal would save around $120 million in the first year, with half of that going back to workers to pay for health care. The unions say that they are willing to negotiate as long as collective bargaining rights are not on the table, saying that savings can be reached through the bargaining process. The proposal would establish benchmarks for costs that would have to be reached by the end of the bargaining process, with any impasse heading to dispute resolution. The plan, which is similar to one proposed by the governor would cover three years.