If you want to take away the ability for the government to pursue the maximum possible penalty, you should also recommend taking away their discretion to pursue the minimum possible penalty as well.
Absolutely. There's no reason why the prosecutor should have any say in sentencing, that's for the judge. And to take that a step further - not only should the prosecutor be unable to pursue the minimum possible penalty, there should be no minimum sentencing in the first place. This is just interference by another route, and worse because the judge can't overrule it even when it's clearly unjust (warning: PDF).
You'll still be addicted, only the cocaine doesn't do anything. So you'll take more of it. Then you may die.
Well, no. This isn't like a speedball where you have two drugs fighting each other - the enzyme removes the cocaine from your system. You're still addicted and the cocaine isn't doing anything, so you take more and it still doesn't do anything. If you take so much that you start to feel it, all that means is that you've exceeded the capacity of the enzyme to break it down and you now are responding as normal. It's still possible to overdose, I'm sure, but presumably more difficult.
Top Ten Things Overheard At The ANSI C Draft Committee Meetings: (5) All right, who's the wiseguy who stuck this trigraph stuff in here?