The idea goes like:

1. We use drupal to compose and store email messages - see #708562: Attribute mapping, the [URL:] PHPLIST placeholder, naming conventions and whatsup for more info
2. Then after composing the node - we use a views exposed filter to choose only the users we needto send to. This will make user attributes syncing unnecessary! Which I think is nice!
2.1. After we filter the users - phplist module creates a new BOOLEAN attribute based on the users who will be the audience for this particular message. And finally:
2.2. We go to phplist's interface (the external php app that is) and in the filtering area instead of using the un-developed filtering UI - we just send the message to all users with the BOOLEAN attribute "issue 23 year 2010 (tag1, tag2)" == TRUE

The attribute's name can be a tag/cck field to the drupal node ctype "issue" ...

My idea is wild but I know it will gonna work- and it will bring COOL features and spare much work to us devs. All information will stay in one place and we will use phplist as a drupal backend.

Opinions?

PS. There still be some syncing with the phplist tables - only over the newly proposed per-issue SEND/DONT-SEND attribute. And only after the exposed filtering is done - on each email issue - one new attribute.