It took several days before the thread was approved by a moderator. During that time I kinda managed to achieve some result but … it's very dependant on tweaking the variables. And it's way too smooth. I am not sure it will work very well with different geo.
What i did was -
1.Used polypath node to turn the meshes to curves
2.Fused them in the middle
3.Extracted the points
4.Fused the points
5.Tried to reorder the points using sort - “proximity to point” but it didn't produce the desired results and the order was still messed up. So i abandoned that option and just tweaked the previous nodes to produce somehow the proper point order.
6.Rebuild the curve
It's kinda working … but not very well.
And this is the result:

Maybe it would be just better to extract one of the mesh edge loops and convert it to a curve but i am not sure how to approach that … And the problem is that the curve that would produce would not be in the middle of the mesh. But at this point i am willing to compromise.
Also it would be good if somehow i can select which points should be the starting points of the curves with a mesh bounding box. A mesh that i extract from the scalp could do that nicely so i don't have to manually reverse the curves that are facing the wrong way.