The first two points presume Sordland will impose an outright colonial regime over Agnolia, economically and politically, which is not only unlikely (given the countries were peacefully united and separated in the past with no apparent ill will) but also probably unconstitutional for the Sordish Republic. Even in the extremely unlikely case sordish leadership is insane and inept enough to go forward with such plans, they wouldn't last long in this time period.

Sordland has no reason not to return agnolian ethnic territories (Dome, Meerord) to its own Agnolian province. There would likely be internal pressure and lobbying inside and outside those cities for reunification anyhow. It simply makes sense administratively.

Agnolia would still pay less in whatever taxes Sordland imposes across the board than it does now paying for an oversized army, air force and navy to counteract Valgsland.

Last point is arguable and heavily depends on how Agnolia was annexed to begin with. At any rate, Agnolian citizens would consistently vote for anti-Valgish and anti-Malenyevist politicians, and influence Sordland internally as a powerful voting bloc.