Create/Save a Profile in ACR that includes a Post Crop Vignette and a selection of other adjustments.
Load Lightroom and apply this profile and all develop sliders work as before except for PCV. The PCV sliders can be adjusted (they are not disabled/greyed out) but have no effect. All other adjustment sliders will work as normal except the PCV slider which does nothing.
Note: In ACR the slider is disabled but there is an additional drop down (set to Profile) that allows you to disable the PCV set in the profile and this reactivates the sliders and allows you to adjust the PCV.