I think that making RakLib an a php exntesion would make it much more powerful and pratical since its api is barely edited.
Making something into an extension doesn't magically make it more powerful. It makes it harder to maintain, and there's also the cost of actually rewriting it into an extension to begin with. RakLib being somewhat inactive isn't because it's static - it's because it tends to get neglected when other things need to be done. With that said, I am working on transitioning some more static and performance critical core components into native code, but this is not trivial and will take a long time to complete. Network components have been considered, but there is only one person doing the work (me). Also, it's a lot easier to have a user update a .phar file than their PHP binary.
It is in fact more powerful when it's an exntesion but yeah fair enough i think people are already super confused with the few required php exntesions to introduce a new one like that, but it shouldn't take as much effort as you're saying.
I will not be surprised if the next thing you say is to have a PHP extension for the whole PM that only uses PHP to load plugins.