I personally think that projects should be expensive to keep nations from growing too rapidly. Part of the thrill of the game is playing for several years and making long term plans to get to your desired size.
If you’re going to allow a member to attack a macro who happens to be in war mode, you’re going to get countered. Life happens, accept your loss and don’t play victim.
It would be interesting if there was a project that would allow you to loot a small percentage of food from enemy soldiers during a ground attack. This would be realistic as an army marching would have some amount of food. This project would be helpful for nations that are always blockaded and that are starving. It would also provide a good source during fallout countdowns.