I don't think the adjacency bonus you want to fit there would a make combat system fun in a 4X (range bonus being the worst part of it), because I've only seen it been fun in games where your defenses are expected to crumble when you start taking hits - or when you don't get hit ever. And because tying that bonus to the scout building would increase the chances of "locking" the current combat system in place.
If you want to give the scout another military bonus, I actually proposed it somewhere above.
PS : also, while I didn't say so in this thread, something bothers me in the current exploration. I can't really pinpoint why yet - but I tend to leave it automated. I don't think it's the point.