If you're looking for moral support for dropping BV as an editor, I'm offering it.
A simple Display View of how it looks, without any ability to edit would be fine with me (assuming it can actually display things like embedded fonts, etc.)
It'd be nice if such a Display View was dockable/separable (for dual-screen use), and if it auto-refreshed -- although I understand that may be difficult with well-formedness checks. A manual refresh would be adequate.
I think you are indeed trying to develop "two, Two, TWO! apps in one!" One for people that get HTML and regex, and one for people who don't -- or don't want always to be bothered, at least.
I wonder if it's even possible to write a "word-processor for epubs" that let's you look under the hood and tinker... Not enough guarantee of regularity to let you be confident of what you're changing when you word-process, especially when importing from external sources.
To keep it elegant, it's one or the other (or both, separately.)