I just took mine out a couple of weeks ago. Obviously, the design is such that those bolts holding down the bar on the front of the seat bracket is load bearing (the seatbelts restrain you in an accident, not those bolts). As such you could probably just use a locking wingnut type configuration to hold them down. Similar to how the hi jack mounts are for roof racks.
I had to cut one screw off because it was rusted in. I haven't yet drilled it out, but you may find similar issues if they've never been taken out. Also, I had to dremmel out one of the seatbelt bolts. Even with the proper Torx (T55 or T50 if I recall), it still was a pain. (Marty, Will, etc. I'll be needing that seatbelt bracket sometime).
I'm contemplating leaving the seats out. I'm not sure yet. I guess the seats aren't too bad, it's really the seat belts that stick up and get in the way.
EDIT:
Glad you brought this up. I actually hadn't thought about converting them to a tool-less quick removal system. But since I've had them out, I really like the setup. Another cool thing is that if you figure out a good mount system, it could double as a securing point for strapping down cargo when the seats are out.