If you really want to create a "new breed" fine. Its been done in the past. In fact, people created all of them at some point. This is NOT what the labradoodle, shih tsupoo, puggle people are doing. This is, however, what the Savannah cat folks are doing.
Here's the big difference. The mutt BYBs are producing puppies for profit or novelty or whatever, but they dont go past F1. They always mix instead of selecting for the dogs with the traits they are shooting for. I have no problem in someone developing a breed of hypoallergenic dogs. Why they dont want a poodle or a portie or something is beyond me, but anyway....I digress. They just need to do it the right way. These people have no idea if what they produce will be hypoallergenic or not, and for ones that have the poodley coat, they dont use those to continue their lines. They go back to the BYB dogs they started with. People dont understand how selection works. That's why you buy a purebred...because you have some idea of what to expect.
Additionally, those BYBs talk a LOT about hybrid vigor. I dont think that they realize that dogs are not that different. There's no guarantee for health in any breeding and when both breeds carry addisons, CHD, etc., you are doing no better by crossing them. Its all a $ thing, and people are suckers.
As everyone else has been saying...if you want a mutt, go to a shelter. There are plenty of great ones there.