Would decreaseing neutral time and increasing capture time work better? For example, changing a 60second captime from 30second to netutral / 30second to capture to 15 netural / 45 second capture.
Makes people clear the area before rushing to get capture moving at next flag.
Reduce the ability / need of people to camp spawnpoints. Makes bots more of a threat, it now has the chance of popping out from random corner firing rather than having 10 ARs shooting it before it can spawn.
Gives reason to stay back and defend.
Punishment fits the crime. Rushing will result in a backcap slowing the game more organically, whilst 5-10min capture time feels more of a forced / punishment for being "good" at offence.
Simpler solution is be the change you want and be the one defending flags.