A state-convened health care panel is recommending that Massachusetts regulate hospital and insurance contracts, a decision that could cause losses and layoffs at the state’s largest provider.

After a dozen meetings over six months, the 23-member panel convened by Gov. Charlie Baker has come up with nine proposals to address the differences providers charge for services.

The final report won’t be submitted until March 15. But in a draft, discussed at a meeting on Tuesday, the Provider Price Variation…