A hex editor built into RText probably won't happen. As for SeaGlass, the last time I tried it, it still had issues, and it looks like it hasn't been updated in over a year. It's unfortunate that nice looking LookAndFeels like that one and WebLookAndFeel
still have issues, and are either dead or updated at such a snail's pace that it isn't feasible to rely upon in a real application.
I've submitted a couple of patches to WebLookAndFeel, and it has real potential, but the author seems to only update SVN once every month or so, and hasn't made some really critical updates that applications like RText, which can swap LaFs at runtime, would require to use it. My patches were "accepted" about 3 months ago, but they still don't seem to be in the SVN trunk even today. So I'm tempted to simply fork the project and make the necessary changes myself, but frankly it's a huge code base, and I already don't have time for my own projects as it is.