Just to note, Moosh uses composer to generate new plugins from templates that are on github and have composer.json files =)
And although you can use Moosh to install plugins for you,
there isn't a way (at least i haven't found) to have a file
like composer.json telling everything you want and just
install eveyrthing with one click.
For what i know, Moosh only let's you install plugins one by one.
I think "you can have a script to do that" is not a reasonable answer.
I've used git repo and git-submodules in the past to try to handle better my colletion of plugins
acrros different Moodle deploys, but composer seems to be better,
even if you need to add a composer.json file or even clone the original code
to your repo to have this file on it while you waiting for the original maitainer
to get convinced of the benefits ;)
FInally, in "container" and "virtualization" times, I've asked people of digital ocean to offer moodle as 1-click-app : https://digitalocean.uservoice.com/forums/136585-digitalocean/suggestions/7606407-offer-moodle-lms-as-1-click-app
And there is a docker image for Moodle (https://github.com/playlyfe/docker-moodle) although it not worked on my debian-jessie with docker 1.3.3 , but fortunately is my fault and not a bug ;D
Kind regards,
Daniel