It seems that central to this topic is the issue of psychology: particular features of Toady's personality dissuade him from taking certain actions that some of us (including myself) wish that he would take. Some of us, were we in his shoes, could actually follow through on some of the suggestions in this thread while not experiencing the same psychological effects that Toady would; we are all simply different people with different personality quirks. (However, to counter-balance this statement, so that people don't accuse me of criticizing Toady, some of these same people might not have been able to do things that Toady has done, again due to differences in personality.)
Toady has said that if he were to purposefully aid third-party interface developers, he would feel obligated to continue aiding them, even if the original intention was for the aid to be a one-time deal. If he obeys this feeling, he has less fun working on DF. If he ignores this feeling, he has less fun working on DF. I can understand this perspective (whether or not I would myself experience it), and it isn't a matter of good or bad arguments or reasoning. It's primarily emotional/psychological, and there's not much that can be done about it, unless Toady himself decided that it was a character flaw that is serious enough that he is motivated to work to overcome it. I don't suspect he'll come to this conclusion any time soon, and I don't blame him. I have plenty of quirks myself that inconvenience other people but that I still don't wish to "fix" (assuming it is correct to call them "broken" in the first place).
Admittedly, I really really really wish that Toady didn't have this particular psychological feature, because I'd really like to see (and perhaps work on) some third party interfaces. But I don't always get what I wish for; that's life. And I don't think there is really any rational grounds to justify to Toady that he should change. So I suppose I'm willing to accept his stance and move on.
Now if anyone can come up with some clever ideas that do not require Toady to purposefully aid third-party interface developers, but that Toady is nonetheless comfortable with, then by all means, we should discuss it. But it seems as though any ideas that require that Toady do anything at all to purposefully aid them (whether it is large or small) are (unfortunately, from my perspective) dead ends for now. There is not much benefit to be had from discussing them.