Since the requested change implies a complete shift in direction and scope, the business case must be updated to reflect the new strategic goals. The business case justifies the project's existence, and updating it ensures all stakeholders are aligned before initiating a new scope or restarting the project.
Option A is reactive and premature without business justification.
Option B is tactical and may follow later.
Option C bypasses critical governance and approval processes.
References:
PMBOK Guide - Seventh Edition, Value Delivery and Governance Domains
PMBOK Guide - Sixth Edition, Section 1.2.5: Business Case Review
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The project manager should have ensured that regulatory compliance, including import regulations for the specific machine model, was considered in the quality management plan. This would involve understanding and adhering to the legal and regulatory requirements that affect the project scope, deliverables, and processes. By integrating regulatory compliance into the quality management plan, the project manager could have anticipated and mitigated the risk of the machine being blocked by customs, thus avoiding delays and potential financial losses.
References:
Project Quality Management According to the PMBOK1
Machinery Regulation: An Essential Guide2
Project Scope Management according to the PMBOK3

According to the PMBOK Guide, agile project management is an iterative and incremental approach that delivers value to the customer frequently and responds to changes quickly. One of the principles of agile project management is to maximize the amount of work not done, which means eliminating waste and focusing on the most valuable features. The product backlog is a prioritized list of features or requirements that the project team delivers in iterations or sprints. The project manager, in collaboration with the product owner and the stakeholders, should prioritize the product backlog based on the business value and the effort required to deliver each item. By doing so, the project manager can ensure that the project delivers the highest value possible within the budget constraints. The project manager should also adjust the project budget and staffing to account for the prioritized items, and communicate the changes to the project team and the stakeholders. The project manager should not balance the project team, restrict the project scope, or reduce the project staff, as these strategies may compromise the quality, value, or customer satisfaction of the project deliverables. References:
* PMBOK Guide, 6th edition, pages 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53...
* PMI-PBA Guide, pages 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53...

In a situation where a significant portion of the project budget has been reallocated, it's crucial to reassess the project scope and deliverables. The Minimum Viable Product (MVP) approach allows the project to deliver the most essential features with the remaining resources. This approach is often used in agile or hybrid project management methodologies to ensure that the most valuable features are delivered first, even when resources are limited. References: PMBOK Guide, 6th Edition, Section 5.4.2.1: Define Scope: Tools and Techniques

In the context of a project that involves new technology and an experienced Scrum team, the most suitable estimation technique is using story points. This method allows the team to leverage their collective experience and familiarity with each other's work to estimate the effort required for tasks relative to each other. Story points reflect the complexity, effort, and uncertainty of the task, making them ideal for projects where the technology is new and exact estimates are challenging to produce. Since the team has a history of successful collaboration, their established velocity can help predict how quickly they can work through the backlog.
: The use of story points is supported by Agile methodologies and is a common practice in Scrum teams for estimating work effort. This approach is detailed in the Agile Practice Guide, which is a complementary document to the PMBOK Guide, provided by PMI for understanding Agile practices in project management. The choice of story points over other estimation techniques is also consistent with the principles outlined in the PMI's Professional in Business Analysis (PBA) Reference Materials, which emphasize the importance of leveraging team expertise and past performance to inform project estimates.