Component video mod

[lnx64]

I was wondering, if it is possible to modify these old televisions to have component video input. When I see flowcharts that show how NTSC is decoded and always see it going to Y, R-Y, B-Y, I can't help but notice that these old TVs seem to use component video internally, since component video is Y, Pr, Pb, which is basically the same.

Is this doable, or is this not as simple as I think it is?