Looking through solutions on the internet, I found that for nginx there are plenty solution for dynamic root directories, headers and environment variables out there.
Today I was asked about using the same application directory with various cached index files, in this case, the determination is based on the domain accessed.
The previous solution used was to create spearate root directories with copies of the same system, which is wrong, just a waste of deployment time and configuration.
A more elegant solution, is to use the $http_host variable, and define a dynamic index file, like this:
index index.$http_host.php index.php index.html;
Now, be aware, this might not always be the best solution. also, most of the times, this will not be the specific setting or variable to use, but the idea is there.