This is a two-fold idea... firstly add a button in the Library > Line Styles screen for "Export" to create a MXL or XML file. Secondly in Magnet Field, the ability to load the Office Line Styles. Then when the MJF is created, the line styles can be assigned to the strings and line features. When the MJF is imported into Magnet Office, the line styles will all be correctly assigned to the incoming data.
Related to this idea would be to include an export to .SHX line type option for Autocad export for drafting. These are already generated with exports to DWG but only contain the shape files for the linetypes in the current drawing, not the whole line style library.