The thumb drive idea won't work on most typical laptops though, where you no longer can disable internal drives in the BIOS. It's funny you mention this, back in the days, I was making modifications of my "special" system for being online, writing it to CD, booting from it, only then connecting to the internet
These days pen drives are so cheap, so I'd rather re-flash a pendrive every day, but keep it writable, or even use a new pendrive each day, like rotating them at some interval to be able to go back to some if I'd discover in a few days that I saved something really important on desktop a few days ago
But the main concept of separating the use cases works well for me. Like in 90ties I really don't care if some day my box-for-fun-things will blow up or otherwise I'll have to wipe it out clean. It's just that, it's for simple enjoyment of using computer and the internet without any fear.