note for other players: if you ban or rare Frankenstein, I will cry. This
is a threat. If the prospect of Frankensorcery terrifies you as much as it does me and you don't have faith that everyone will leave this particular M.A.D. device alone, the review button is the perfect fix. (It could also use clarification on how the process of creation works—is it a 0-cost quickplay card that creates, but does not play, the fused Frankenstein? Or is it an X-cost card that lets you pick the components you want to a maximum of X stars, then play the result "for free"? I think the former has less potential for abuse, though it'd have one notable advantage over the latter.)
One breaker would be using it on Divine Lambitures in the GY. So if it hits three, you get nine numbers out at minimum, or Nine stars. Replay at your leisure.
Getting nine Numbers out of a Frankenlambiture would actually require all six Divine Lambitures in the graveyard, since Frankenstein exiles the ones used in its creation and doesn't become a Divine Lambiture itself. (Its name doesn't change, and Divine Lambiture's effect refers to itself by name.) You could get decent results starting at four Lambitures, though.
Canyon being a card you don't usually want to play, but gives you a star and clogs up your hand might be OK. It's a reasonable point that half of the theme of the cards is the nonsurprise, with effects on hand reveal. In that sense, it's no more powerful than a Cosmic Isopod. Maybe even slightly worse.
You know, a 0/1 quickplay stargen blocker is actually pretty strong for a 0-cost card. Maybe even too strong. Maybe even stronger than Generous Gift. Hey, you know what we should do? We should unban G