Multiple issues

[Selur]

"...forcing Hybrid to not use mencoder" - how?

You can't really to it. Hybrids code needs to be changed to support this.
Only way you can work around this in Hybrid would be to:
a. set "Filtering->Support" to "Avisynth"
b. enable "Config->Avisynth->Always use Avisynth"
when you want to encode a DVD to something with interlaced output.
(Alternatively use an Avisynth or Vapoursynth filter, this way Hybrid will use Avisynth or Vapoursynth for the DVD input processing.)

Cu Selur