Vi Plugin Design Patterns

Hi there, I wrote the ViMate plugin for TextMate v1 back in the day. It's been killing me not to have Vi commands since TextMate v2, and since it's open source (i.e. far easier to write for) I was considering writing a new vi mode for it. I could modify my old code as a starting point but was wondering if any of you have settled on some good design patterns to consider when starting a vi emulator from scratch? Surely with so many implementations some design patterns must have come to the surface. Thoughts? Any advice is greatly appreciated. Thanks! Kirt