If humanity were governed by the Frontier Militia from the Titanfall universe and their territory existed in the lawless regions of the Mass Effect galaxy, it would cause them to expand and eventually control a significant portion of the Terminus and Traverse upon first contact to the point to be considered a major power. This is how relations might fare between the council members of the Asari, Turians, and Salarians and their respective governments.

In this hypothetical scenario where humanity, governed by the Frontier Militia, expands and controls a significant portion of the Terminus Systems and Traverse in the Mass Effect galaxy, relations with the Asari, Turians, and Salarians—the three major Citadel Council races—would be complex and potentially tense. Here's a speculative analysis of how these relations might fare:

Asari:

Cultural Differences:

The Asari, known for their diplomacy and biotic abilities, may initially approach the situation diplomatically. However, the cultural differences between the asari and the Frontier Militia, which consists of a diverse and sometimes unconventional group, could lead to misunderstandings.

Concerns for Stability:

The Asari might be concerned about the stability and governance of the expanding human territories in the Terminus Systems. The potential for conflicts and the Militia's resistance against external control could raise eyebrows among the asari leadership.

Resistance to External Influence:

If the Frontier Militia has successfully resisted external influence and control in the Terminus Systems, the Asari may fear that attempts to exert influence or diplomacy could be met with resistance. The Militia's commitment to autonomy might be perceived as a challenge to the traditional influence of established powers.

Turians:

Military Concerns:

Turians, being a militaristic species, may view the Frontier Militia's military strength with a mix of respect and wariness. The Turian Hierarchy could monitor the situation closely, especially if the Militia's expansion threatens Turian interests or violates established norms in the Terminus Systems.

Potential for Alliances:

If the Frontier Militia proves itself as a stable and formidable power, the Turians might explore diplomatic avenues or consider alliances based on shared interests, such as resisting external aggression.

Militia's Combat Effectiveness:

If the Frontier Militia demonstrated exceptional combat effectiveness during the Frontier War with the IMC, it would showcase the ability to successfully engage and resist the Turian Hierarchy, it would raise concerns among the Turians. The fear might stem from the realization that the militia poses a formidable military challenge.

Potential for Turmoil in the Terminus Systems:

The Turian Hierarchy might fear that the success of the Frontier Militia in unifying various the Terminus could lead to increased instability and turmoil in the systems and council space. The Hierarchy may be concerned about the militia's ability to influence other factions and encourage resistance against established powers.

The shift in Power Dynamics:

If the Frontier Militia emerges as a major power, capable of challenging and defeating Turian forces, it could alter the balance of power in the region. The Turian Hierarchy may fear losing influence and control over territories they traditionally considered theirs as the Unification War could possibly restart as Turian separatist factions might become inspired by the Militia's history.

I could possibly see the Hierarchy being severely afraid of the Militia and being heavily worried about security because of never having dealt with a civilization that never incorporated eezo into their technology, a civilization that uses AI, developed alternate forms of FTL travel, and an organization that descends from a loosely governed set mishmash of homesteaders, criminals, bandits, mercenaries, terrorists, and pirates all rising up as 'citizen soldiers' which later formed a government after the events of Demeter.

"Bunch of upstart colonists waged a war of rebellion against their homeworld, and worst of all, they won!"

Unknown Capabilities and Intentions:

The unknown nature of the Frontier Militia—its capabilities, intentions, and leadership—could contribute to the fear within the Turian Hierarchy. The uncertainty about how the militia would govern and influence the Terminus Systems may create anxiety among Turian leadership.

Salarians:

Analytical Approach:

Salarians, known for their analytical thinking, might take a pragmatic approach to the situation. They could assess the Frontier Militia's capabilities, the geopolitical landscape in the Terminus Systems, and potential opportunities for collaboration.

Unpredictability:

The Frontier Militia's nature as a decentralized alliance of diverse factions might make them unpredictable. The Salarians, who value strategic planning and information, could fear the difficulty of predicting the Militia's actions and responses in diplomatic or military situations.

Cautious Engagement:

Salarians may engage cautiously, analyzing the benefits and risks of interacting with the expanding human territories. If the Frontier Militia demonstrates stability and resource management, the Salarians might find areas for cooperation.

Common Fears:

Potential Alliances:

The Asari, Turians, and Salarians might fear the Frontier Militia's ability to increase their dominance by forming alliances within the Terminus Systems. If the Militia manages to unite various factions or gain the support of other species, it could create a united front against the established powers, challenging the influence of the Asari and Salarians.

Resource Control:

If the Militia controls a significant portion of the Terminus Systems, including vital resources, the Asari and Salarians might fear economic repercussions. The loss of access to resources or trade routes could impact their economies and technological advancements.

Diplomatic Challenges:

The Frontier Militia's decentralized structure might pose diplomatic challenges. The Asari and Salarians, accustomed to dealing with centralized governments, could find it difficult to engage in traditional diplomatic negotiations, potentially leading to misunderstandings or conflicts.

Potential Shift in Power Dynamics:

The rise of the Frontier Militia to a major power could signal a shift in the power dynamics of the Terminus Systems. The Asari and Salarians might fear a loss of influence and control over the region, especially if the Militia gains popular support among various species.

Ideological Differences:

If the Frontier Militia operates with a different set of values or ideologies, the Asari and Salarians might fear the imposition of unfamiliar principles in the territories controlled by the Militia. This could lead to cultural clashes and challenges to established norms.

Common Themes:

Resource Interests: All three races would likely be interested in the resources within the expanded human territories. The Terminus Systems are known for valuable resources, and the Asari, Turians, and Salarians may want to secure access or establish trade agreements.

Security Concerns: The Citadel races would have concerns about the security and potential threats emanating from the Terminus Systems. If the Frontier Militia can assure stability and control within their territories, it might lead to more amicable relations.

Overall, relations would depend on the actions and policies of the Frontier Militia, as well as how effectively they can manage the complexities of governing an expanded territory in the volatile Terminus Systems. The Asari, Turians, and Salarians would likely approach the situation with a mix of caution, curiosity, and a pragmatic assessment of their own interests.