I personally think that
1. interlaced video is a past, it's something like VHS now
2. every Intel's or NV's user have an option to do high quality HW deinterlace right in the video decoder
Would it be hard for SVP to "export" motion information for other filters (or e.g. madVR) to reuse?
Right now SVP is just an Avisynth filter.
Link with avisynth.dll, run the script, feed it with video frames and you'll get motion vectors from the SVAnalyse function.