Makes sense! Have you considered Ansible?
Configuration management systems like Ansible and Salt and Puppet are fairly rigid; they are basically modular recipes for placing files and starting services on remote servers. What you get from Mesos (combined with its frameworks) is something that can run your services, keep them running, and handle the several state transitions that affect any running application: Transitioning from one version to another, for example, or restarting a failing app.
We've tried using supervisord as a stopgap solution, but it, frankly, sucks. Doesn't follow forks (no cgroups), isn't capable of cleaning reloading its config, can't do master/worker replacement, doesn't support syslog in any meaningful way.
The nice thing about Mesos etc. is that it makes almost no assumptions about what your system is. You pick and mix the functionality you need. For example, Marathon is basically just a process manager. You wire it up the way you want; the application can be anything, from a web server to a one-off script.
Kong seems to be "Rails for microservices". Which is probably useful to someone, of course.