Ahh, yes, this seat would want a simple post hole structure and would probably not work OOTB (out of the box) with the Simplex post you mentioned. I believe the C17, or other Ideale or most other seats would work with the two tube structure.

On the MAFAC I found, in the photo, the hood was hard plastic and not removable. There might be other functions, but offhand one major one is riding with your hands high on the handlebars/brakehoods. When standing up off the seat and over the bars it is nice to position your hands there. Not sure how that would feel without them? One other bikes, I have replaced old ones with newly manufactured ones (Cane Creek comes to mind) that should not be too expensive.