Zaha Stair - How to create an alternating set of lists to define profile curves for a stair case detail

Hello,

I have set up points on a stair case and I would like to use a list to single out 6 points on each stair to create an interpolated curve which will then be used as guides for a loft, as indicated in the rhino screen shot below.

 That in itself isn't difficult, but I would like to set up a list or series of lists that can be used for the entire length of the stair case, to create the same profile curves. My end goal is to end up with something like this:

Ideally I would like this to work with a curved profile wall, hence the emphasis on points. Is there a way this can be achieved through grasshopper alone? 

Thank you.

RIP