Glad you qualified this is not a UK construction otherwise the immediate response would have been to get it re-designed (also take it your company cannot afford to walk away).

Could one end be left open so that stitching moves up in ever ascending layers between the panels - installation of the next level up being completed from the one below?

Very much depends on the design of the cage; you can get a domino effect whereby if one rib collapses during re-stitching they all do.

Working at height (access/egress to cage)

Rescue controls would be similar to confined spaces, i.e. tripod and man at top.

Weather conditions, miniscule chance of lighting strike, but still need to be part of your assessment.

Earthing  arrangements potentially high risk depending on your environment, you might need to consider a earth spike bonded to the cage, you certainly need to consider other nearby metal structures.

Hand/battery tools only.

I have seen rebar cage collapse first hand (concertina within a shaft like dominoes).  One of the main issues is that the inherent stability of the cage is in the finished state, not the temporary (unfinished) state.  Temp Works designs rarely consider supporting the rebar structure during construction.  Previously within our organisation this was managed by the construction team in an ad hoc way dependent on their experience.  Although you suggest no re-design is possible, it would be advisable to ask the design team to indicate how temporary supports can be factored into the design.