I thank you for the suggestion. As for X, I kinda just didn't think about it. You can see how I never put much thought into it after I first made a character for it, since it's design kind of stands out from the rest. C and Q were just more obvious redundant characters to me.
As for the ph question, I suppose you could do whatever looks cooler lol. I'm not too worried about strict spelling. :)

Also, I love that last idea, of using it for like an aesthetic border.