Is the point of the x-spells to be a free counter? If so, there is a risk of running into them again and wasting the turn. The probability of running into one of the 12 x-spells is much larger than the finishers. If tutors aren't banned in this format (Idk, I don't play lots of magic) then you should run a playset of both tutors instead of the x-spells to ensure you get what you need (
Vampiric tutor and
Mystical tutor). Also, tune up the big creatures so you run into them more often. I don't play much modern, so take what I say with a grain of salt. But this is a cool idea!