I think if someone was to redo TeX, that it would be really nice to see an incremental type setting system. That means modularity not just at the code level, but also with respect to how the run-time data structures are dependent on each other, and the ability to "reflow" text on a change in a way that required minimal changes to the previous flow of the text. Then we could have something that was Wysiwyg, interactive, and produced output that looked fairly decent.
Ok, at least as good as TeX then, something much better than Word. I mean, we are getting good with doing incremental computation (e.g. FRP, SAC, etc...), why not apply these techs to the problem of typesetting.
