If you have $150, use MainConcept MPEG Encoder
http://www.mainconcept.com/site/?id=825
fully supports batch mpeg-2 to mpeg-1 encoding
(don't forget about de-interlacing for interlaced video)
TMPEGEnc v.2.5x (free mpeg-1 encoder) not supports MPEG-2 file opening, but with DGMPGDec freeware you could create *.d2v files, which could be used for mpeg-1 encoding with TMPEGEnc - it will not be batch mode.