REVERE ? A new investor in the Suffolk Downs said Monday he envisions a world-class horse racetrack and casino enhanced by restaurants, retail outlets, live entertainment and family activities all part of the same resort.Richard Fields, chairman and founder of Coastal Development Massachusetts, has acquired a “significant interest” in the racetrack. He previously co-developed the Seminole Hard Rock Casino and Hotel projects in Tampa and Hollywood, Fla., with the Cordish Co. Those resorts opened in 2004 and continue to flourish.”Richard Fields’ investment in Suffolk Downs is a positive development for horseracing in Massachusetts,” said Suffolk Downs President John Hall. “He’s an avid horseman who brings extraordinary enthusiasm for racing as well as considerable expertise in gaming and development.”The investment makes Coastal Development the largest shareholder in Sterling Suffolk Racecourse, the company that owns and operates Suffolk Downs.Fields said the first task is to develop a master plan for the resort, which straddles the Revere and East Boston border. “Over the next few months, our team will be pursuing a master plan that allows us to integrate the horseracing that has long defined Suffolk Downs with a world-class facility for everyone who visits.”A rancher and conservationist, Fields and his wife, Meeka, own Jackson Land and Cattle Co. in Wyoming, and are involved in bringing agricultural education into the region’s schools through Farm Aid and Wyoming Agriculture in the Classroom (WAIC), according to Suffolk Down spokesman Chip Tuttle.Al Balestra, president of the New England Horsemen’s Benevolent and Protective Association, sanctioned the investment.In addition to Fields, the racetrack’s primary shareholders include partnerships controlled by Joseph O’Donnell, chairman of the Boston Culinary Group, Vornado Realty Trust, and Hall Properties.