I was just starting building my own Blog system hack for vb, but something came up and I'll be busy with some other projects, and since you are porting an existing one and adding new features to it, which should be better having one official Journal's system for all of us to use.
Here is a list of stuff I got in mind so far:
Journal
Journal display options (Journal Index Page) - sort by, sort order, from date
Journal and Entry subscription (Notification on new comment or entry by email optional)
Active Users viewing Journal / Entry
Who viewed my Journal / entry
Journal status icons: New Entry Indicator
Weekly / Monthly calendar with highlighted days and navigation for Archive
Admin tools for Journal - edit/delete/lock/Make sticky/ etc
Email page to a friend option
Top Journal page: most commented, visited, rated, favorite
Journal, Entries and Comments Moderation
Standards Compliant. should supports XHTML 1.1, CSS 2.0, RSS 0.93, 1.0, and 2.0, Atom 0.3. Supports conditional GET for caching RSS feeds on the client-side
Search Engine
Rating System
Lock System
What's New: Link for recent Journal, Entries and Comments
Entries
Linear, Threaded, Hybrid display views available
Links to next/previous entry: Allows viewing the next/previous entry when viewing a single entry
Supports BB Code in entries (Optional)
Supports HTML in entries (Optional)
Smilies
Avatars
Moods: Allows members to add their current mood or moods to entries
Photoblog Entries: Adds a single image to an entry (Optional)
Define Entries BgColor: Member can specify bgcolor to an entry (Optional)
Members can choose to post drafts, not publish to the front page
Optional WYSIWYG or standard editors for entries and comments
Entry Types (Optional)
Quick comment box (with optional "forced" click on comment to quote)
Preview entry option
Entry rating
Polls
Entry Reporting - report entries to moderators
User post count
View Single Entry
Admin tools for Entries and Comments - moderation/edit/delete/ etc
Quick delete/edit Link: Adds a edit/delete links to the footer of each entry and comment