First of all, thank you very much for taking your time to answer me.
My first message was posted just a couple of days after discovering Rex, but since then I have tested it pretty extensively.
Recently I've started to work on a side project (meaning unsolicited) inside my company, which I believe (and hope) that will change how the company deploys its software into production. Today all the process is done manually, but this is totally unsustainable in the long term.
So far, I'm amazed with how extensive Rex is, meaning that it helps automating the hole process with the flexibility that Perl code gives. Previously my company tried to automate with Ansible, but it wasn't customizable enough for us to use.
Long story short, I'm far from giving up on Rex :)
Regarding the box that I requested, I opted for making such pre-made machines with Vagrant in combination with Rex, and although I haven't developed much that functionality yet, it promises to be a good solution too.
I really appreciate your interest and help, and it's awesome to know that this software in which I have so many hopes put on is actively being used by other people around.
I would like to stay in touch with you, in order to share experiences and get support from each other if you would like to do so.
Thank you again for your time!
Regards from Uruguay.