I have climbed the Haiku Stairs twice.  Let's be quite clear, this is not for everyone.  That there have not been any major accidents - well, Thank God.   If the Stairs were re-opened:

1.  There has to be a control regarding the physical fitness of the people who would be allowed to use the Stairs.   Proper attire - primarily footwear - is a must; e.g., rubber slippers are dangerous, in this case.
2.  Better control of when the Stairs can & can't be used.  The stainless steel ladder can be shrouded in the clouds or rain making visibility almost nil, and the rails of the ladder quite wet & slippery.  Also, it can become quite chilly.
3.  "Does the City & County want to invest funds to make the Stairs safer?"  I would guess, in light of the overruns in the mass transit, that the answer is, "No!" 

Sections of the Stairs are attached to the Pali face; vertical & 100's of feet above the ground, with no safety net.  The potential for danger is there.   How to improve & better control?