Currently, some guilds have to limit the number of flags members can complete to give everyone a chance to attack. This makes it impossible to get enough points to complete the rewards for the majority of players. Both making these decisions and abiding by them are unfun activities.
I suggest that once the fortress is complete, reinforcements are sent in. Maybe 10 rows (or all of them if it’s easier to code) refill. No guild reward should be given for these, so there is no pressure on non-elite guilds to keep up.