Doing some major network changes, would be nice to do some sort of bulk "release / renew" via Group Policy.
Is there a way to do this
As Zoredache mentioned in the comments, setting the lease duration to a shorter interval is probably the simplest method. That being said, you might be able to script something up that uses psexec against either a list of known machines or something generated out of a subnet scanner to run the commands. Test it on a few systems first :-)