How would American history have unfolded if the US and Confederate governments ruled that WV couldn't break off from Virginia (US explanation: we still own the state so the Constitution applies so existing states can't be broken up, CS explanation: we own it and don't want to lose it).
At the very minimum, as time went on, we'd have WV forced to VA's allegiance in the Electoral College because presumably VA's population is much higher than WV's so they'd probably dominate Virginia's population (though I haven't checked this).
Another possibility is this: WV secedes during the Civil War and is glommed back onto the state by the Union after the war.