Don't use webkit view

Webkit has great features for wysiwyg editing. Writing rendering engine from scratch would take a lot of time and duplicating Webkit's features.

grvrulz tried writing vapi for Abiword engine, but he didn't succeed. Abiword as renderer is probably the best choice for this project, so if someone manages to write vapi for AbiWidget (http://www.abisource.com/wiki/AbiWidget) we will use it.

Actually I don't think basing it off of Abiword or even LibreOffice would be a good idea.
Focusing on open standards is important and when choosing your rendering engine you should also be mindful that newer formats like Apple's iBook, Amazons Kindle Format 8 or the International Digital Publishing Forum's epub3 formats are all based on html5.
Looking at a feature matrix of these formats and lets say .odf leads me to believe that in order to get libreoffice or abiword capable of reading them they would essentially need to make them into fully fledged browsers at which point you have to ask yourself another question, which rendering engines actually take up the most resources and/or time to start right now anyway.?
I'll give you a hint, it wont be webkit :D
Gtk_TextView is not feature rich enough and you will need to spend allot of time trying to get it there(years) at which point you will have a browser again :D lol
I think you made the right decision going with a webkitgtk webview and hopefully we can get some epub3 support. I think it would be wise to focus on supporting the formats listed above over outdated legacy formats like .odf and .docx.
I am aware people will thin its crazy calling them legacy and will most likely complain but epub will be supported out of the box on the most popular platforms today(iphone, ipad, android phones and tablets, .docx and .odf are not). In terms of formats epub1,2 and 3 should be of primary concern as they are open standards. ibook and format8 would come next.

If you want to Use libabiword, I've asked for adding GObject Introspection (and also vala binding)

http://bugzilla.abisource.com/show_bug.cgi?id=13369

There are also vapi on Internet.