I think there are good way around that, like having the font outlined with a different color or making the background less translucent closer to the characters.

A keyboard like that could be designed with multiple layouts to space the characters out more. Like a full keyboard, alpha, numpad, etc, with the modes faded out around the current one (eg by default you have alpha, and click a faded box to the right to access the numpad). Blah, I'll stop trying to explain what's in my head, but I support the option of a translucent keyboard