“Functional equivalent” as alleged here may or may not be viewed by courts as a basis of action. It may be that the political process, or an even more specific legislative process specifying what due diligence must be, is the only way to oust such a governor or prevent his actions.
Depends on how those four Supreme Court justices view what he is doing and whether they are willing to order an injunction.
McAuliffe’s public statements may be admitted as evidence of his intent in what he is trying to accomplish in individually exempting all or most of the felons. If the four justices conclude that McAuliffe is trying to do indirectly what he was prohibited from doing directly, then it is likely they will enjoin him. And his public statements sound somewhat damaging on this.
One analytical approach would be to say that in order not to be an abrogation of valid law, exemption must be not only individually-based but exceptional. Under this analysis to exempt a majority of felons, even on an individual basis, would be to nullify legislative intent and would be beyond the power of a governor.