mixing and matching of HD and SD source material in the same timeline?
 

Does anyone know of any other solution than Media 100?
Thanks for the time and consideration should anyone answer.

This works in Final Cut Pro,
Set the sequence to the resolution of what you want to output, HD or SD. Clips of either format will work in either sequence. FCP will scale down/up the clips to the size of the sequence, you can then resize them to fit your needs.

This works in Premiere 6.5 and Pro also.