BNA Tower Controller reported they vectored a Medical Flight helicopter and departing air carrier away from an unidentified VFR aircraft orbiting just outside of their Class C airspace.

Narrative

Aircraft Y was receiving flight following; MEDEVAC status; from the southeast of the Tower airspace to west / northwest at 1600-1700 ft. Aircraft Z was departing off BNA turning to the southeast to climb above Aircraft Y. I; in the Local Control Position; observed a VFR target approximately 6 miles southeast of BNA; north bound indicating 1300 ft. He turned away from the Class C airspace at the last moment and started doing orbiting right in front on Aircraft Y's flight path. I attempted radio contact and did not succeed. I attempted contact on guard as well; no successFinally; the VFR aircraft not in communication with ATC called the Departure Controller who gave him a squawk code and affected coordination with the Tower Controller in Charge to let me know who he was and what he was doing. During this time frame; before the Departure Controller could tell me; I had to turn the departing Aircraft Z to stay on runway heading to avoid the VFR. I also issued traffic and had to turn Aircraft Y who eventually reported him in sight and advised me he was a helicopter. The VFR traffic turned out to be Aircraft X who wanted to land at BNA. This VFR aircraft went into an orbiting holding pattern in front of MEDEVAC traffic and right in the departure corridor for BNA. This is legal and EXTREMELY dangerous. We desperately need to fix this airspace! We need a Class Bravo IMMEDIATELY!!