Sounds like ScanTo3D is what you need (part of SW Premium).
It is easy enough to write a macro to create a 3d sketch containing the points, but it will still be very slow
ScanTo3d is designed for exactly this requirement.
You may download free macros from myIntercad.myToolkit (please find the info in my signature) to import the text points to 3D sketch. Please search for ‘Import Points’, ‘Import LIDAR data’ under the translators section.
You may slightly modify it to create lines or splines rather than points.
Artem Taturevych, Application Engineer at Intercad (Australia)
translationXpert – add-in to translate SolidWorks models
myIntercad – an integrated tool for SolidWorks Professionals