I thought the FIA was
committed to bringing the halo (or some alternative) in this season, so the designers really should have factored this in from the start.
Given that the alternatives were discarded fairly promptly after testing, the halo looked like the most likely option and the specs for it were well known over a year ago.
If anything, if they had decided to postpone the halo or select an alternative, it probably would have been more destabilising.
