This would work similar to the "Alternate podcasts" option, but would work better when different podcasts release with different frequencies.

Currently, if Podcast A releases weekly, but Podcast B releases monthly, the Alternate podcasts option when sorted by date will produce a playlist that goes:
ABABABAAAAAAAAA

Instead, it would be nice if the two podcasts could be "spread out", so the playlist is:
AABAAAABAAAABAA

Thus, rather than greedily alternating strictly at the beginning of the playlist, they are distributed so that they alternate over the entire playlist. This would prevent the problem of getting to the end of the playlist and having just a dozen episodes of whatever show releases the most frequently.