It makes sense for Inno to make a GB for people who negotiate. There are a lot of people at all ages of the game who do it.
I guess, I'm one of them!
At least at some of the live serves, I play all content (GEX-64 / GBG) by negotiating only. Why? Well, because I want to and because I am able to! Therefore I did not build the Himeji Castle there and I'm very happy about the Space Carrier, which is more or less the same as HC for negotiations, as far as I understood!
If so, I prefer getting supplies instead of medals in eras below Arctic Future Age, because those help a lot, in lower ages especially.
As already stated
..., the fighters are a little bit favored at the moment, aren't they?
... and getting medals instead of supplies would be just another disadvantage. On the other side, I would not mind giving HC the same effect as the Space Carrier, which is producing "
special resources every 24 hours after reaching the Arctic Future Age (like Promethium)".