Hmmmm.. Well, we have to see what the rewards will be and if it's worth building it.. But it's somewhat strange mechanic to add, because we are limited to what and where we can negotiate.. Unlike battles, where you can just attack some neighbour for daily if IE, BG, continent map, etc are not available at the moment.
I see BG as the main source for negotiation because it's available to you for most of the time. But still, we have a few days break from BG.. Same with IE, if you finish that in 1-2 days, there is nothing there to negotiate.. So negotiations are not always available to us, unlike battling.
On mars continent map we have the opportunity to negotiatite for mars ore, so that is pretty much always available. I guess that would be our "permanent" source of negotiation (and maybe there will be a similar mechanic on the new continent map). But that's not gonna work out for people in lower ages who build their GBs earlier
Oh well, have to wait and see how lucrative till GB will turn out.