FWIW, a few weeks back I proposed changing C-z away from suspend-frame for a similar goal, and got generally negative feedback about gui versus terminal differences. The proposal also involved C-S-z, which doesn't work in some terminal environments, so that probably skewed feedback somewhat.
From experience, I've been rebinding C-z (to a keymap) for around 30 years now, and stopped having any trouble with it around 27 years ago. (At the time, I would frequently use both hardware terminals, especially vt-100, vt-101, and vt-220's, and sometimes DOS or OS/9 systems with serial modems.)
In practical terms, I suspect the conflict between "C-z is SIGSTOP" and "C-z is undo" is the biggest fault line between "typical personal computer users" and "unix-ish users", and thus is effectively a "third rail" of Emacs HCI discussions. That might just be pessimistic assumptions talking, though.
~Chad