Sorry about this time. I didn't explain anything of what I thought and just wrote my feelings about it.
My mind is dumb sometimes.
I think I understand how it would work and what you proposed. I find that an adjacency bonus of +1 range to be completely OP and therefore would not work, ever. From what I've seen in the game, it seems to allow free attacks with no possible retaliations, requires a complete rework of the spawn mechanic and of the rogue mechanic - as those IMO are heavily tied to the range of attackers and defenders. A "max" range limit would help, but I fear not enough. And, in addition to the military buildings, it would require scouting buildings everywhere, basically, because if the game is "tailored" toward having this bonus the player will be underpowered without it. So probably be on average at least 1 scout station / military building or something.
Therefore I explored the idea of targetting with a 1 target limit as an heavy nerf to your idea. I don't come out of it convinced. About that part I supposed like for a lot of buildings there was a population cap or something, but after testing in game there is not.
Is that clearer ?
Too bad about fog of war.