If mencoder or something like that is available, we can probably use the tablet-encode script and run it after downloads have finished (code for hooking up scripts after a download finished is already available, as "cmd_download_complete").

You can:
1.) Install mencoder/tablet-encode
2.) Write a script that uses the environment variable "GPODDER_EPISODE_FILENAME" to decide wheter or not to convert the file (is it a video file or not?) and then also convert the file
3.) Make this script executable
4.) Set this script in the advanced configuration editor to the variable "cmd_download_complete".

This should work. If not, simply make a script that you can run manually that will search through the gpodder download folder, find all video files and convert them using tablet-encode or something similiar.

tablet-encode can be found here: http://mediautils.garage.maemo.org/tablet-encode.html

What do you mean with "select podcasts by bandwidth/resolution"?