Why not have your local tests, automated or not, cover the common cases and error conditions to catch programmer stupidities? Then let the actual humans do the strange corner cases.
If your design is even close to correct, testing repeatedly tested code is pointless. If your design is corrupt and your implementation is sloppy, no amount of testing is going to save your ass.
I do very rapid turns and I am a one man team. I can turn my system in less that 30 minutes and have the user testing it in a live situation on the other coast. If I want 10 turns a day, I can easily do it. Low coupling, high cohesion, clean correct design, and disciplined implementation makes it possible.
I agree that doing things in small chunks is a great way to do it but doing the equivalent of a weeks worth of global automated testing for each small change seems like a silly exercise. That is except for the server hardware salesmen and system admin people.
The sales commissions and payroll look rather good. The production of real value is questionable. Bang for the buck is as important for testing as it is in any other part of product development.
I have found from working in large teams, there is a core four who get things done. The rest are simply dead weight dedicated to shuffling paper and attending meetings. At best, they do nothing. At worst they create more work than they do.
Use the right four and dump the other sixteen. You will get at least ten times more productivity and ten times higher quality without even breaking a sweat. If you don't have the right four, you are hosed from the start.
When you begin to take that into account you realize you have to find ways for the larger team to work together and still produce a quality product. Hence the techniques being used by the author and other companies out there trying to address similar problems.
I am not sure its possible. The communication overhead of so many linkages forces incoherence. The resultant incoherence forces still more additions to process and body count. That adds still more communication overhead. The result is still more incoherence - not less. If something is "finished", its simply because time, money, resources, and toleration ran out. The end result was simply called "done".
Maybe that is the best we can do but I am hard pressed to call products produced that way quality products. See Vista et.al. for instructive detail.