Hi, I may be a bit late replying to this. I hope not. The move could be great, but you have not explained what the steadicam needs to do after the step off. This may allow us to suggest a safer way to do the shot. A couple of questions:
1. If the camera is looking straight down, the steadicam op. is going to struggle to hold the frame.
2. How do you plan to keep the track out of shot if the track distance is so much greater than the arm?
3. Absolute no, to a steadicam operator getting off backwards off a moving crane. There are complicated issues when you allow a step off a crane. The arm is counterbalanced. At 30 feet arm length you are looking at a payload to ballast ratio of atleast 1:5. If someone stumbles, trips , f#$@'s up - you will have dead people on set as the ballast comes crashing down with a half tonne (atleast) and the crane does a back flip. The step off and securing is going to require some choreography and at least 2 static seconds on the ground.
I have done this kind of move successfully several times, and I have more white hair on my head because of it every single time.
As darryl recommends, a big truck based crane would be ideal. But that will be dictated by terrain.
As far as location cranes go, my reccomendation will have to be the Giraffe Long Ranger from Filmair. It is the only one that will get you the length and stability that you need.
Forget about the steel, hand built crane. A steel 30 foot crane will be so heavy that pushing it at 10 MPH and then stopping it and controlling the arm will be a serious task.
Lastly, and in my opinion most important. Get the best Key Grip money can get you to pull off this shot safely. Things can go horribly wrong very quickly.
Having said all of that , with the right people and the right tools, the shot can look fabulous.
Good luck and be safe!!
Tell us what you decide