NGINX DOES support having configurations in many files through the 'include' directive. Basically, it loads a sub-configuration and put it in place. It also supports joker characters, so it's easy to load many of them in one shot.
The only limitation (in my opinion) is that you need to reload when the configuration is changed. So any user who has a piece of configuration might need rights to reload nginx config:
/etc/ini.d/nginx force-reload (on centos)
I don't really know if there is a way to avoid that or to do it differently because I use NGINX on many servers with lots of apps(virtual hosts) which are my own. It would mean that NGINX is not ideal on shared hosting.
Nevertheless I really love NGINX because configuration is just so much more legible than a nasty XML file. Question of taste I guess. The other good point is obviously speed, if it's important in your case.