I kind of agree with you. Trying to get people to not to take the path of least resistance is a hard task.
IMHO ht need to figure a bigger carrot and not a bigger stick to get people to change sides.
Keep eny in place but figure a bigger bonus for people who make an effort to jump sides.
Like free perk rides for your first 2 sorties or some such.
Don't think there is a fix for it.
People are people, human nature is human nature.
Majority seem to prefer to fly with their squad.
You also have to assume that the overall country numbers in the player base are roughly equal, and are spread out the geographical regions fairly equal, which I don't think they are.
For example prior to the arena split you could watch through the day and tell which country had the numbers in certain geographic regions. Used to be Knits had numbers in the early mornings (Europe), then during the day Bish would catch up and overtake them (US) then late evening it was usually the Rooks.
Try balancing that between 3 countries in two different arenas and I think you're on a hiding to nothing.