Andrew supplied patches to filempeg.c and dvdcreate.C to allow for Bottom Field First interlacing for DVD creation. This has been checked into the GIT source. In addition, the Manual has been updated on how to do this (basically use the Settings->Format option to set Interlace Mode to Bottom Field First before starting the DVD creation from the DVD menu).

May be you can control bitrate and interlace flags in cingg manually, too:

Look for xml file in upper-right corner of batch render window, open it in editor before hitting start, look for vmpeg specific params for mpeg2enc module, edit them, save xml file in editor, start render. (not tested just idea)