your 140 approval notice is buried in an HR drawer and nobody would have time to touch it unless you leave the sponsor after a big ugly fight.
Most of Americans couldn't differenciate illegal and legal, temporary visa and green card. It's unlikely for some employer to go that distance to revoke an approved 140.
On the other hand, even if your first 140 sponsor doesn't revoke your 140, there is still chance that an ignorant USCIS employee wouldn't port your first PD after your second 140 is approved. If that's the case, you still need to communicate with USCIS many many times.
By the law, the 1st PD is yours after the 1st 140 approval if there is no fraud.