I've read most of the thread, which has some interesting suggestions mixed in with the usual AOW discussions along with other topics. So the OP asks why not a one dive course that's a lot cheaper than AOW-- for "seniors" of diving? 1,000 over 35 or so years is like 30 dives or so a year. Since ALL are logged, diversity of the dives is known (I know, someone else could show up with fudged totals, etc.). If someone does thousands of dives for decades without logging, SOL. In the case of the OP, I would assume at least the last 200 or so are recent enough that they could actually be checked out and confirmed if someone so desired.
So, how about this. The AOW card certifies you to a recommended depth of 100', thus all the "charters won't let me dive without it" discussions. I did AOW with 2 post OW cert. logged dives and learned a fair bit. To take the Instructor or Self Reliant Courses you need 100 logged dives. So, you set a number for anyone wanting this "quickie" AOW-- 500 or 1,000 dives perhaps. There would be some form of Knowledge Reviews, or a test, or both (none of which costs class time). The one dive required has to be Deep of course. Buoyancy of a 1,000 dive diver would of course be perfecto (that's the PPB Adventure Dive done). Some basic compass navigation (if you can do a square, which may take 3 minutes, you can certainly do a reciprocal heading and count 40 kick cycles, etc.). You'd have to throw in some other stuff because you still need to cover the other 2 specialties, but which ones? (another big topic). There may be other options for some, such as one tech. dive to 200' and call that his AOW. So, one dive, a fee to correct the test comes to what, $100 or less as the OP suggested? Then again, that's just about the price of a full tank of gas where I live. Now there would be of course the important point of the Instructor's fee/pay. After all, they are trying to make a living and it is their time taking these experienced divers through the motions. Maybe it's even something a DM could be now qualified to administer (and they get paid a lot less or not at all-- so I've heard). And there is the money that the shops would like to make. All the details would have to be ironed out by those who do that at PADI.
Now why in the world wouldn't PADI want to set up such a course? Oh, somebody already explained that.