[quote=@Scarifar]
I don't think it'll work. There aren't many monsters whose ATK changes upon Summon. Not even Phase Shift monsters, since their "printed" ATK and DEF values are ?/?. I'm not really sure what that means, but my interpretation is that they don't have an original ATK value. 

So, I think this card is rather useless, really.
[/quote]

?/? Is 0. But it's the way I intended to use the card in the first place, since I have two monsters who DO do that.

Also changing attack could also mean stuff like "When this card is X summoned, have it gain X attack for each of it's X materials"

edit: also there are PLENTY of cards that are useless in YGO. I run one. Self-Mummification, you'd have to be REALLY niche to run that thing