Possible minor changes for gyms

Ok, so Ill see if I can follow this up and justify it in your terms, assuming we are talking sieges, the idea of your walls, forts, castles etc would be to preserve and protect what is inside it however this was never limited, arguably these defensive structures also had the potential to provide clear offensive benefits with height and protection for things such as archers, traps to limit the enemies and heavy placements within the walls, you would also have a "home field" advantage by arguably knowing the area better than your opponent, so your surroundings were also likely to give you numerous advantages small advantages too. I feel I should say just like a siege the offensive side has much more choice in how to go about things, their advantages is their flexibility, which as you pointed about before could be argued the limited movement is a parallel, also the fact the attacker gets to choose what they attack with to give themselves their own advantages, but even with limited movement it should be argued the defenders would have numerous advantages in numerous areas with their biggest downfall being attrition (a continuous siege) which relates to prestige.

I think that would be an accurate representation however because a siege isn't so black and white a clear correlation cannot be made, there are far to many factors and this game isn't based around medieval sieges.

To sum it up, a wall or fort is set up with numerous straight up advantages for the defender, the attacker chooses how to get around or counter it.