Rather than cut benches (which the rig would have to traverse over) probably better to raise the levels so that the commencing surface for piling is at the highest level?
Here in the UK, the relevant guidance document is BRE470 - working platforms for tracked plant. This recommends level piling platofrms. Ramps for rig travelling over the plaform should not exceed 1:10.
I've recently looked at a project for a 2km long pipeline with poor ground conditions, where formation of the piling platform is a very large cost, and spoke with a number of rig manufacturers to see what slope a rig could actually operate on.
I was looking at the use of a Soilmec SF50 in CFA mode, and a Juntan PM25 rig in driving mode and both can operate at a slope of up to 3 degrees.