I would argue that there is just as valid a reason for Epiphany as there was for Gnome. Epiphany was created after Galeon (another Gnome web browser that nobody used).

Gnome worked to create Human Interface Guidelines, and wanted a web browser (which is a fairly fundamental part of a desktop environment in this day and age) that used those guidelines to provide a cohesive experience.

Here was an announcement email which explains some of the reasons for it's existence:

http://mail.gnome.org/archives/epiphany-list/2008-April/msg0...

I would say that options 2 and 3 that you propose are nonstarters.

I feel weird that I've found myself in a position defending Epiphany. I don't mean to be, it's a shitty browser.

I just don't find it puzzling that a desktop experience project would want to be in control of their own web browser which uses their own underlying technologies.