The following sections of our Director documentation [1]:

7.3. Scaling the Overcloud
7.4. Removing Nodes from the Overcloud
7.5. Replacing Compute Nodes

Should have corresponding troubleshooting sections that cover what to do in the cases where what is described above does not work. 

In general, the troubleshooting in Chapter 9 is focused on "day 1" problems with standing up your overcloud but not "day 2" problems with keeping your overcloud running. Starting your install over again in these scenarios is not acceptable if the recommended procedures don't work since you might disrupt a production overcloud. Thus, being able to troubleshoot these scenarios without disrupting the overcloud is important. Could there be additional entries in Chapter 9 on troubleshooting problems from 7.{3,4,5}? 

[1] https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux_OpenStack_Platform/7/html/Director_Installation_and_Usage/index.html