Think about it...before GE was introduced...what was the chief guild based complaint? "we don't do GvG, our guild treasury is a waste".
If BG is done right, meaning it has depth, a great battle element, and benefits a guild at least to the equal extent as GE, then why do GE.
GE will always have a place with newish players, cause it helps them as much as the guild. But for seasoned players, especially GvG players like myself, GE is..well... boring. I do ot as a labor of love for my guild, but it's just that..a labor.
If BG is as taxing on my guilds treasury as GvG..or near so. And as beneficial as GE, of near so. Then GE will become moot. This is the case for alot of players man, read the BG thread comments.
With the exception of newer players, GE is boring, it's not a challenge, and the newer event buildings have devalued it's rewards greatly.
I'm not saying it will be removed from the game, because it won't. But it'll become stagnant and stale. Therefore getting no further development attention, nor should it. It has served it's purpose, and ran it's course.
As for the OPs GB idea..I like it. It's just behind it's time.