Well the downside is that it would take more effort to develop and it takes away from the devs to sell the revival potions. Aside from this I would say it's not sure how fun this actually will be wile getting rather random cards that might not have the best synergy. So it's possible to much improve on it with additional layers to the draw.
Thanks for the comment!
Having to create working teams out of random cards is a big challenge - I'd see that as part of the fun :-D
I actually also think this would be the case, in a way synergized decks with freedom is something that cal be done in Wild and Modern. I also like the idea of excitement when seeing what cards you get and also the fact that it allows everyone to actually experience all cards. Now, I (and most players especially new ones) never really will experience playing with Kitty or all the Rebellion Summoners let alone at max level as it's simply not affordable or convenient.