Note that I don't really use or edit podcasts in Musicbrainz so take my opinion here with a grain of salt.
I do however like to tag stuff which is similar, namely tracks which are released over time in a blog-style format (e.g. Jonathan Coulton's "Thing a Week", #13root's "Evil Morning", Party Ben's mashups...)
I think there are two things that would be most useful for this format:
- Tagging of recording-series in Picard.
- Giving a series entry a "number" based on date rather than a serial number. This is probably technically possible now but the interface is not built for it.
But I think this reflects the reality best, in that there are often no good demarcation points ("volumes" or the like) to group the recordings into releases, and the release date is at best a fiction (I have used the date of the most-recent track but that doesn't really help for the others).
Treating them all as singles should also work, though some people likely won't like how that clutters up the artist's page. So probably some work on how such things are displayed would be in order as well.