I think flipping is a waste of time and would rather just play the game... but that's MY opinion. If people enjoy flipping, then do it. You bought the game to play it your way - your money, your time.
I will never be affected by this 20 card max, and I think it's better to have super expensive live series cards. The collection should be and end goal, not something that needs to be done in the first week. But at the same time, you have to let the market be what it's gonna be. Once you start trying to control certain aspects of it, it goes downhill. There's absolutely no reason to limit someone from having any number of cards. I also think there shouldn't be set price min/max for each rarity. Let cards cost what they cost, and let people buy what they buy. Imagine owning a small house in a sought after area, and only being able to sell it for 100k, because that's the forced limit of houses that size? Not the greatest example...