Can you provide a link to the mid-80s California DUI law? Because outside of capital cases, statutes which actively preclude alternative and judge-designed conditions of probation are exceedingly rare, and I would be astonished to see that California's mid-80s DUI law was one of them -- especially given that "creative sentencing" wasn't the issue then that it is now.
I think it would be incorrect to assume that if the law doesn't specifically allow for a judge to impose her own conditions for probation, then she is forbidden from doing so. The allowance of "broad discretion" mean just the opposite of what I think you are proposing. It seems that you are suggesting that whatever is not expressly permitted is implicitly forbidden, when in fact the opposite is true -- as the cases I cited demonstrate. Does the statute expressly forbid ignition interlocks or any other judge-imposed "special conditions"?