If 8 is possible. Why not?

I think that would be too bright compared to the buttons. As it is now, when I went from three to four, the knob is already starting to look unusually bright compared to the buttons

I'd rather see someone figure out how to mix the plastic in such a way as to diffuse the light more instead of trying to brute-force it with more LEDs. Four is already overkill, I'm sure it could be done with one LED if only the plastic could do more diffusion.

(Not that it looks bad right now... I think it looks really cool as-is, I'm just saying if we're adding more LEDs to diffuse the light more, we're approaching the problem from the wrong end.)

I know it can be done because I've seen it done on other types of plastic and rubber buttons on electronic components... I have a big TV remote that lights dozens of buttons with a single LED. I'm sure it's just a question of finding the right compounds to mix.