As requested, I've gathered some of my notes on the Empire’s border states to establish some more concrete lore. If anyone knows of any inconsistencies, please link to any posts or comments that establish precedent. If anyone has feedback, their own ideas, or contributions to share, please do so here and we can make canonizations and retcons!

Map Link (I know the countries are referred to as "Kingdoms" here, but I figured more diverse governments were more fun.)

Sabati:

This is actually an Imperial city under the control of a rebel group.

(From the wiki) The Female Liberation Front, despite its name, is the most moderate of the rebel factions. It aims only to end female slavery in the Empire and have equality of the sexes. Because of its equal mindset, it has a number of male supporters, and a significant stronghold in the Empire’s cosmopolitan northeast, including the city of Sabati – the only major city in the Empire to be controlled by rebels. Sabati’s Imperial unit defected to join the rebels and establish the self-proclaimed Northeast Free Territory, which operates much like a tiny Western nation. The FLF operates as part of the NFT’s military, and has not engaged in offensive action for some time. They are well-equipped, having inherited much of their equipment from the Sabati Imperial Guard unit. Because of this, among other reasons, the Empire has no intention of invading the NFT at present. However, blockade measures are increased around their territory for security reasons. Although the Empire does not actively capture members of the FLF or NFT, members of either who enter the Empire are unlikely to return. Rogue soldiers who attack the Empire are treated accordingly. NFT men found in Imperial territory are given a standing offer of settlement in the Empire, with a reasonable residence and welfare provided by the Empire. Cunts who wander into Imperial territory are taken into custody and given a gentler slave training before being sold into slavery under a more allowing master, for the sake of good relations with the NFT. Most adjust well to their new status.

Rotalia:

Rotalia is a military dictatorship that arose during the Gender Wars. Wanting nothing to do with the politics of the conflict, the city declared martial law and secured the surrounding region with intense defensive lines. When the Gender Wars ended and the Empire emerged, Rotalia asserted its independence and further reinforced its borders. The ever-present fear of invasion by the Empire, especially from its female citizenship, ensures that the Rotalian Military remains in power.

It's current head of state is a female Grand General with an expectedly inimical view of the Empire.

Tolo:

Tolo, similarly to Rotalia, ratified its government as an independent state in the fallout of the Gender Wars and fortified its borders. Unlike Rotalia, Tolo was somewhat more involved in the gender politics that led to the conflict. Although their laws are ostensibly egalitarian, their culture is often seen as matriarchal. Women tend to hold higher-paying jobs, play more executive roles in household decisions, and are often subtly favored by the legal systems.

Its government is a more conventional democracy presided over by a Prime Minister.

Midland:

The largest and most developed of the border countries, Midland is renowned for its citizens' rights. While the Empire suffers many international sanctions, Midland's clean public image grants them a very favorable international standing. Many conspiracy theories surround its relationship with the Empire, the most popular of which is that the state is, in fact, propped up and supported by the Empire as a buffer state through which the Empire launders its non-slave imports and exports.

A portion of Midland, the Angler Peninsula, was captured by the FRA years ago, and currently serves as their central stronghold. Midland still recognizes the territory as its own, and has made no significant efforts to displace the FRA since the invasion, creating a difficult diplomatic situation for the Empire were it to invade to combat the FRA.