Industrialized single device installation for personal use

For years I've been using a script to reconfigure my personal system & I was wondering if perhaps there's a better way to "industrialize" & structure my device installation. I install the OS manually & every time I run my script to reconfigure it to my liking. But having to maintain this script that's now 1000+ lines long is getting burdensome. Ideally I'd like something simple like: 1. Install OS. (Debian) 2. Install reconfiguration software with 1 command. 3. Run reconfiguration software with a provided config in 1 command. 4. Remove reconfiguration software. 5. Enjoy. Having the least amount of overhead is what I'm looking for, I don't mind if the creation of the template configuration takes a while, but once I'm installing the system, I want it to be straight forward & simple. Most of the options I found all required a server, agents or complicated setups. I'm looking for something as simple as a script but, cleaner & more maintainable. Would anyone know of software for this task & those requirements? Preferably open source. EDIT: The gist of it is a configuration management software that follows the KISS principle when it comes to it's use on a personal device, however the making of the configuration template can be non KISS.