WP Engine does not support mounting your WordPress installation into the sub-directory of your domain for a single site installation. In other words, no more domain.com/blog or domain.com/etc. If you have a WordPress installation that is going to share a domain with another website then we recommend using a sub-domain set up like blog.domain.com.
Note that the subsites of Subdirectory Multisite installations can be mapped to domain.com/etc, but we wouldn’t recommend a Multisite configuration as a means to accomplish this goal.
Having your installation live in /blog is not recommended for various reasons. Traffic would need to be proxied over from the original server, which means if the server for your main site goes down, so will your WP Engine site. In such an event, we wouldn’t be able to support the outage. The same holds true to any latency that may be present on the main site’s server, or in the connection between the two servers..
Additionally, using the /blog configuration on our platform will bypass several key features that we implement, most notably the Staging site and One-Click Backups.
Please be aware, if this type of configuration is absolutely necessary, we will not be able assist in setting it up. Additionally, we’ll be limited in the amount of support we can provide for your site.
We do understand that there are a good number of users that prefer this configuration; however, we strongly recommend converting over to and using the sub-domain configuration. This ensures that you have full control over your site’s DNS, and you can make full utilization of our support and special features!