What you've got is how every MMO on the market that has Qs for PVE and PVP do it. I know it seems to make your arguement more valid (even tho it really doesn't) to make it seem like they were simply to lazy to come up with the Q but not really in the Q idea of stacking. Under this solution you'd still take forever to get a FP Q to pop cause PVP pops are dime a dozen and you'd have a cloud of perpetually stuck people in the limbo in-between the two. Dan is #19 and gets out of his PVP Q and gets another 30 seconds later, so he has a whole 30 seconds for the PVE Q to pop before he's back in limbo again.
How is this in anyway a workable solution? How much of the games resources are going to be tied up keeping track of the massive cloud of people in the Q but not really because the are in a PVP match at the same time? Yes eventually they would get lucky and get a pop inbetween the two but in the meantime the only reliable way to get in a PVE grp is too...not Q up for another WZ...just like they are asking you to do now.
You raise a valid point, but this could be solved by simply letting a player know where they are in queue. If a queue would have popped for them while they were in a wz, let them know so they can refrain from queuing for another wz. I'd suggest that once a fp queue would have popped once for them, it would make sense that if they queue for another wz at that point, they be taken out of fp queue because otherwise people may just sit in fp queue at the top of the list for an indefinite amount of time.