I like the intent behind this, because I absolutely agree that successfully defending an invasion should matter beyond simply retaining what you already had. In hindsight this also helps alleviate the fear of factions being chain-invaded to burnout to some degree. Where I hesitate is making automatic defender territorial gain the standard consequence.
Narratively, it doesn't make sense for a defender to suddenly end up new lands and peoples for holding down the fort. I think that risks creating some unhealthy incentives for the map game. If every failed invasion can immediately cost them an equal amount of additional territory, I could see factions becoming significantly more reluctant to attack at all. Instead of encouraging the map game, it may encourage people to tuck tail and turtle. Considering how much OOC investment, judging, and general contention can already surround invasions, I am not sure giving the defenders the same territorial benefit of the attacking factions to make those situations healthier.
I think the better answer would be giving a successful defense meaningful consequences for the attacker without immediately handing the defender territory. Attackers should get penalized. For example, losing an offensive invasion could create a temporary vulnerability, neutralize hexes in between - creating a buffer zone, or altogether prevent that faction from immediately launching another invasion for a preset time based on the gravity of the invasion, give the defender some form of priority or advantage in launching a counteroffensive, or create a limited window where the defender can pursue the retreating faction into connected territory.
That creates something I think is much more useful narratively:
Attack → failed campaign → retreat/disorganization → opportunity for counterattack.
Now the defense actually creates another story rather than simply resolving the map result through an automatic hex exchange then sit decisively. It would also make offensive decisions matter. If you throw your faction into repeated wars and lose, eventually there should be consequences for overextension. At the same time, the defending faction would still have to do something to capitalize on its victory rather than receiving territory automatically. To me, that would help the map game more in the long term.
So TLDR: I am very much in favor of making defense more rewarding, I would just rather see the reward help In-Character story instead of just benefit Out-Of-Character actions.
