Thanks very much for the advice. I would love to use a lift but the customer doesn't want anything driving across all his walkways and wires, he wasn't even hearing it. After looking again today, I think the safest bet is to do the cribbing and drop it on the ice, over top of the wall. This will leave me looking very unprofessional, and have to walk out on the ice and collect all the bits. There were lots of new branches on the ground today... I may not have to cut it if the wind blows good tonight! Maybe I should pass after all.
Getting a hazard tree down safely, and predictably, without damage...that's the plan.
If the homeowner wants it more difficult than need be, he just has to pay more than need be.
Two days ago, I was at a house for some easy ornamental pruning where a few months ago I had a dead, dead bigleaf maple in a fancy, landscaped stream gully, with stone walls up hill, and super expensive low-voltage electric lights (somehow, the replacement bulbs cost $98 each?!!??!!, which the homeowner is reverse engineering for $2 bulbs. They have about 50 of those. Guessing the stream gully has $50-100,000 of landscaping/ hardscaping. He removed the lamp fixtures in the drop zone for me.
I built up logs, 2 on the base, one on the top, like a triangle, with trucker straps holding them together. One pile above the lower wall on the gravel driveway, one pile below the upper wall on the gravel driveway, and cut it from a springboard at 9' to clear the wall and impact on the logs and driveway.
My crane-operator is seemingly always in a rush. I kinda didn't want to try to unlace a tangled, dead crown over first, myself, and second, fancy landscaping where everything that falls will show and need cleaning up, with him in a rush.
Dumped it onto the piles. Easy clean-up, skidded the logs up onto the driveway using alturnamats (plywood wood have worked).
No impact. No crane rental bill. No coordinating to be there in advance of the crane to be set-up.
For the top 15' of a tree, I'd bet you could get a post hole digger, put two post/ logs in the ground, and a log across the top, in front of the wall. Dump it on that, to protect the wall. Two pieces of plywood across the top of the wall for insurance. All re-useable.
No climbing, no rental machines. Cheap and easy, unless the wall is very tall. My guess is that with a view property, there isn't a castle wall and moat.