Curioussly works only one face side for me...

so

Scale 1000
Copy only one faces / Curves of the object
Rebuild all curves of this one side (one by one) 10 points
Make Planar 2 big rounded planes rounded faces extremities
Loft all the rest little curves
Shell all the faces ...Center Lines 100
Fillets 20 :)
Works fine! But maybe not the more speedy :)