Developers who re-invent/re-imagine some wheels usually realize at the end why the original wheels are designed like those. We, understandably, don't quite appreciate the work other people have done, where we consider their tradeoffs as mistakes. But when we do them ourselves, we eventually see the huge amount of conflicting goals, as tradeoff is the essence of engineering, or anything.

However, almost all the good new things came from some re-invention. Don't let the tradeoff scare you away from your original ideas. Maybe the whole interface doesn't beat what we have now, but there are quite a few very good stuff in your demo. And I believe some of them (zoomable overviews, widgets), can truly work better than what we have now. It somehow reminds me of Rob Pike's Acme editor, though they look very different.