Depends on the target platform: if you think just PPC/AROS maybe there's room for improvements (eg. fast syntax recognition needs some processing power).
If you aim to 68k mostly, I think that going better than present choices is difficult or, at least, would take a quite long time of coding for comparing with leading products (the classic Cygnus Editor, GoldED, etc.).
But if you feel to do it, do it anyway!

BY!
P.S. I'm thinking about doing a basic QR code decoder (from images): pretty useless on a fixed system, but why not, and I want to do some coding as well!
