Well, quite an old post but here is the solution for this.
For C++ There is a function inside RotatingMovementComponent that let you rotate actors on a different pivot point but since there is no Quaternion inside the blueprints solution is I came up with is adding a rotating movement component to the pawn and give it to camera’s location as its pivot.
I know it is not a proper solution but it is working just fine.
With this, you can rotate your HMD locked camera in place. As I said not a proper solution for blueprints but working just fine