Wow! Cool idea. I'll have to give up the idea that I can listen to every episode of every WP podcast. :)

It would be worth including CommPress by Troy Dean and Video User Manuals. There's also a new podcast coming sometime from Bronson Quick and Jason Resnick called WP Dev Table.

In terms of filling in time, you could also have a segment where some of the old episodes are played. It would be interesting to hear podcasts from 5 years ago again, including some of the retired ones (WP Podcast, etc).

As far as creating mobile apps go, not against the idea as such, but it may be simpler to leverage existing apps such as TuneIn Radio (ie get it listed there so people can listen through that).

Cheers,
Stephen