I've thought about this, but it just doesn't seem likely that something like 30-40 guppies could reproduce fast enough. Guppies just are slow. Live bearing just seems like a very inefficient process compared to egg laying.
Of course, they also have to survive the force of the filtration system and that's another matter altogether when you have small fish in a huge tank. I use to routinely find smaller guppies in my HOB.
And assuming you have a huge number of guppies at the start, (e.g., 100), at some point, a lot of fish might ignore the smaller fish. It would make a good thread if you use either method though, so I'm looking forward to seeing the results.