Performing a risk assessment of the access rights is the best way to address the concern of conflicting access rights during the integration of two companies. A risk assessment will help to identify and prioritize the threats and vulnerabilities that affect the access rights of both companies, as well as the potential impact and likelihood of information exposure. A risk assessment will also provide a basis for selecting and evaluating the controls to mitigate the risks. According to NIST, a risk assessment is an essential component of risk management and should be performed before implementing any security controls1. The other options are not the best ways to address the concern of conflicting access rights during the integration of two companies, but rather possible subsequent actions based on the risk assessment. Reviewing access rights as the acquisition integration occurs may be too late or too slow to prevent information exposure. Escalating concerns for conflicting access rights to management may not be effective without evidence or recommendations from a risk assessment. Implementing consistent access control standards may not be feasible or desirable for different systems or business units. Reference: 1: NIST SP 800-30 Rev. 1 Guide for Conducting Risk Assessments 2: M&A integration strategy is crucial for deal success but remains difficult: PwC 3: The 10 steps to successful M&A integration | Bain & Company : Cracking the code to successful post-merger integration

"An information security training program should be tailored to the specific roles and responsibilities of employees. This will help them understand how their actions affect information security and what they need to do to protect it. A generic training program that is focused on policy, business processes or recent incidents may not be relevant or effective for all employees."

When recovering a compromised system that needs a complete rebuild, the first step should be to restore configuration management files. Configuration management files are critical for identifying the system's original state and the changes that were made to it, and restoring them can help ensure that the system is rebuilt to its original state.
According to the Certified Information Security Manager (CISM) Study Manual, "The initial phase of the recovery process requires that configuration management files be restored. These files represent the foundation of the system and provide insight into the original state of the system, which is important for identifying changes that were made to the system as well as ensuring the recovery process can return the system to its original state." Patch management files, network system logs, and intrusion detection system (IDS) logs are also important in the recovery process, but they should be addressed after configuration management files have been restored.
Reference:
Certified Information Security Manager (CISM) Study Manual, 15th Edition, Page 256.