Good luck, but I'm rather skeptical of your project. My own take is that something designed to do two jobs doesn't do either one of them well. I gave up on my multi-tool because the knife blade was too short and didn't lock, the scissors didn't cut very well, the tweezers weren't pointed enough to be effective,and I never used the other gadgets. I now happily carry a locking knife, folding scissors, and good pointed tweezers.

You can probably design such a combo, but I'd bet it won't carry comfortably because the suspension won't be sturdy (it would have to be pliable for the tent application) and (with all the seams for the pack and the fact that it would almost surely have to be single-wall tent) it will either leak or suffer from terminal condensation - and the Pack-A-Tent will end up weighing more more than a separate tent and pack put together.

Like I said, I'm skeptical, but I still hope you pull it off. The only constructive thought I have is that you might be able to overcome the suspension issue by incorporating the sleeping pad into the pack as a "framesheet." That may well limit the load-bearing capability, though. Be sure to let us know how it turns out - preferably with pictures.