When faced with dissatisfaction from a stakeholder, it is important for the project manager to listen actively and demonstrate empathy. This approach aligns with the PMBOKGuide's emphasis on effective communication and stakeholder engagement as key aspects of project management. By listening carefully, the project manager can understand the concerns and needs of the functional manager, which is crucial for maintaining a positive relationship and ensuring project success. Additionally, this strategy is supported by conflict resolution techniques that prioritize collaboration and problem-solving, as outlined in PMI's resources on managing project conflicts12. References: PMBOKGuide - Sixth Edition; PMI's "Managing Conflict in the Project Environment" article2; PM Study Circle's "5 Conflict Resolution Techniques in Project Management" blog post1.

According to the PBA Guide, one of the techniques for managing stakeholder engagement is recognition and rewards, which can be used to motivate and appreciate the team members for their contributions and achievements1. The PMP Exam Content Outline also lists recognition and rewards as one of the tools and techniques for leading a team2. Awarding certificates of appreciation is an example of recognition and rewards that can boost the team's morale and performance. Informing the team about the delivery pressure from the project sponsor may increase their stress and anxiety, which can negatively affect their performance.
Sending a formal notice to team members instructing them to maintain performance may be perceived as a threat or a punishment, which can also demotivate the team. Hiring a few temporary team members to help with the additional work may introduce new risks and challenges, such as communication issues, learning curves, and integration problems, which can delay the project further. References:
* 1: PBA Guide, Chapter 6, Section 6.4.3.5 Recognition and Rewards
* 2: PMP Exam Content Outline, Domain II: People, Task 8: Lead a team

To ensure a smooth inclusion of new subcontracted resources, the project manager should share the project team ground rules with the subcontractors. Here's why:
1.Clear Expectations: Sharing the ground rules helps the subcontractors understand the expectations and requirements of the project team. It provides clarity on how the team operates, communicates, and collaborates.
2.Alignment: By sharing the ground rules, the subcontractors can align their work practices with those of the existing team. This minimizes misunderstandings and ensures consistency in project execution.
3.Avoid Conflicts: When everyone follows the same ground rules, it reduces the chances of conflicts or friction due to differences in work styles or approaches.
4.Effective Collaboration: Ground rules cover aspects such as communication channels, meeting schedules, reporting formats, and decision-making processes. When subcontractors are aware of these rules, they can actively participate and contribute to the project.
5.Documentation: Documenting and sharing the ground rules creates a reference point for all team members, including subcontractors. It serves as a common framework for collaboration.
In summary, sharing project team ground rules with subcontracted resources promotes a cohesive and efficient project environment.
References:
*PMI, PMBOK Guide, 6th Edition, p. 357
*PMI, PMP Certification Exam Outline, p. 9
*Additional Reference: ProjectManager - Client Management Skills
*Additional Reference: Mural - Understanding Client Needs
*Additional Reference: Birdview PSA - Client Management Skills

The project manager should inform the sponsor and document the request in the stakeholder engagement plan, as this is the best way to handle the situation without compromising the project scope, budget, or schedule.
The sponsor can then decide how to deal with the key stakeholder's request, and the project manager can update the stakeholder engagement plan accordingly. This will also help the project manager to maintain a positive relationship with the key stakeholder and avoid any potential conflicts or misunderstandings.