Dave, my comments are moderated. But I'm emailing you, too. 
Thanks, Dave. I'm glad you understood the spirit in which I bloviated. I certainly see the merit of wanting to not re-invent the wheel in terms of your choice of a development environment. And since you know its powers, you have awesome development tools at your disposal. There certainly is not anything else like it.
But I can't shake the feeling that you must have something more up your sleeve. I mean, if you don't want a Radio blog, there are powerful blog engines out there. Are you so frustrated by their interfaces that you wanted to create another blogging tool? If so, all I can say is ... wow!
Ditto for aggregators. I mean, you (and I mean you, personally, were you to use FeedDemon) could have created a "River of News" style for FeedDemon with all the bells and whistles in about an hour. Really! It's about as complicated as a stylesheet. Although, you've gone back to Mac now, so maybe that's not a great example (FD is Windows-only).
My point is that you're pursuing this with such overwhelming force that I can't believe all you want is a new blogging client and an aggregator.
As far as improvements and bug fixes, from what little I know about Frontier, it looks like everything except what's under system.compiler.kernel can be changed. So why don't we start a bug hunt and a feature request list? I'll happily host a bugtracker. And here's an improvement that could be made to the OPML conversions.
BTW, hope you don't mind the informal tone of address. ;)
Am I Amazed or Confused? 
I'd like to think I'm having an "Ah Hah!" moment, but I'm actually feeling a bit confused.
Fact: Dave Winer founded UserLand, which developed Frontier.
Fact: Dave has been instrumental in popularizing blogging and podcasting, as well as related publishing formats RSS and OPML and web services technologies XML-RPC and SOAP.
Fact: UserLand made the Frontier kernel open source.
Fact: Dave developed and released the OPML Editor as open source software.
Fact: The OPML Editor is based on the Frontier kernel, and it implements many (but not all) of its capabilities.
Fact: The OPML blog - which initially seemed to be the whole point of developing and releasing the OPML Editor - basically has become irrelevant. The only significant OPML blogger is Dave, and even in his case, he primarily uses it as a blog of his other blogs.
Fact: Dave developed (and continues to develop) a tool to turn the OPML Editor into a generic blog editor. Initially, it only worked with WordPress. Currently, it should work with just about any blog software with an XML-RPC interface.
Fact: Dave developed (and continues to develop) a tool to turn the OPML Editor into a generic "River of News"-style aggregator.
Fact: I love the OPML Editor as a note-taking tool - a note-taking tool that automatically synchs to my server with the help of my ftpUpstream script.
Query: Why is Dave developing yet another blog editor and yet another aggregator?
Query: Why is Dave developing these tools on a platform (i.e., Frontier) that is so esoteric?
Query: Is there any way I can make the OPML Editor handle strings, files, datastreams, etc. as UTF-8 by default rather than ASCII? (Okay, that's not really relevant here....)
Hypothesis: Dave Winer is trying to leverage his knowledge and a small developer community to develop "something big." He believes the Frontier platform is well-suited for stealth development because it already possesses vast capabilities that few know about because the object database structure of the kernel is so damn inscrutable, and the developer community is small. Re-implementing a blogging tool and an aggregator serves the dual purpose of (1) meeting his personal desire for tools that do what he wants and (2) reinvigorating a dormant developer community.
The Big Question: What is Dave's next big thing?
P.S. - I just figured out how you can control iTunes from within the OPML Editor, including library and playlist management, as well as player controls.
