That certainly hasn't been my experience in many miles of riding our tandem solo without any extra weight on the rear of the bike. The tandem used to be our commute vehicle so if I ever needed to go somewhere during the day I'd hop on the tandem by myself. Applying the rear brake could be an issue since it would skid rather easily with the light load on that wheel, but using the front brake was never an issue. Also used the tandem to climb some particularly steep (but fairly short) hills since the low gearing on the tandem let me pedal up them whereas I'd be forced to walk on my solo road bike. Definitely had to use the front brake a lot on the way down - but again, it was never an issue and the tandem handled fine (although a bit truck-like) when ridden solo.

To the OP:
I know it's been done before since I remember reading an article about someone setting out on a long (round the world?) tour who was choosing to use a tandem for its ability to carry lots of luggage within the long wheelbase. But I wouldn't choose to use your proposed design. For one thing the extra weight burden seems excessive - the tandem itself probably adds 15 or more pounds compared to an equivalent solo bike, the large number of couplers add some more pounds, and the two hard cases plus packing material add still more. So you're probably at least 50 lbs. over the typical bike tourer.

And then there's the bulk of the package you're proposing. A tandem is trouble enough to transport, but consider if you ever find the need to hitch a ride or take public transit with a tandem plus two full-size suitcases (yes you could do the disassembly and packing - but in my experience with other's coupled bikes that's a rather lengthy procedure - and you still have two big and heavy pieces of luggage to deal with plus whatever you now have to carry the rest of your gear).

An alternative to fully self-contained touring incl. airline luggage would be Bike Friday's system using a folding bike that tows a trailer frame on which you carry a regular Samsonite suitcase with your gear inside. Ride to the airport and the bike and trailer frame fit inside the suitcase after you take out the gear and pack it in your carry-on duffel. That way you only have one big suitcase, the bike packs more quickly (and folds enough for transit systems in only a few seconds), and the trailer disconnects quickly leaving you with a nice riding and maneuverable bike for city sightseeing when you stop somewhere for a day or two. Or, if you really don't want a trailer then something like a Big Dummy gets you the long wheelbase and luggage carrying capacity but without going all the way to a tandem length and weight.