@GBr Folks have tried to use portage in the past for embedded distros with somewhat mixed results. Building everything from scratch is a good idea (Yocto uses that concept with bitbake), but it can take several days to build a complete distro with portage. It just depends on what you're used to I guess. I know folks who love portage. I've not had enough time on it to give an opinion one way or the other.
For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This discussion will examine what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.