I think this is a great idea, it's simple (one karma = one minute) and it addresses many of the problems I foresee with this new rules, in particular getting stuck in "pending limbo" indefinitely (given that you can't post if your previous comment is still pending).

It still makes it take extremely long for a new user to obtain 1000 karma, though. Much harder than previously, I imagine. Although maybe not, since there will be less posts visible, those that are will get relatively more karma points?