To insure the passenger receives the best helicopter flight for there money, the company would refine there tour flightplan over the course of a year, 2 years or how long they've been in business.
Therefore, expect to receive the best helicopter tour available with the selected tour on hand.
If you wish to make arrangements for a custom helicopter tour, then you'll need to look around the heli services available for the country or county/state you wish to take the tour.
Not a lot of helicopter companies make changes to there tour for various reasons. First, it takes time to schedule a flightplan; second there's areas that are restricted to fly over.
So if you wish to make a custom tour - and a handful of services do - then be sure to shop around.