Giving your opponents access to an extra 2-4 mana during their second main phase can definitely be problematic if your opponent is holding a powerful card or two, but in exchange, you can snag 4-6 each turn, as no mana is given out when you lose life
Some, like Crackling Cyclops, grow stronger with each noncreature spell you cast, while others, like Balmor, Battlemage Captain, buff every creature you control
Under the current rules (as of writing this blog post) both of them would simply die as a state-based action due to the planeswalker uniqueness rule, so nothing special happens
Our first combo wincon is piggybacking off a card thats already in the list Professor Onyx
2023-11-10 Any choices made when the ability resolves won't have been made yet when it's copied
This already makes Stock Up the best option for card advantage/selection in formats like Standard and Pioneer, but when you consider the formats that include free interaction the value gets ramped up to 11