Even if we wanted to switch to "i" we'd have to continue to also support "j": there's a ton of existing code that uses it. Since "j" is used by some fields (including my own) for the imaginary part of complex numbers, and since I don't think we want to have two ways to do the same thing, I think this proposal should be objected.

But if you really want to pursue it, I suggest starting a discussion on the python-ideas mailing list.