I actually had the same idea, while playtesting I found out that the drawback of having another non-blue source, which is not casting your
cryptic command, is worse than the benefits it gives. The thing is, either
cryptic command taps all possible blockers, or royal scions gives you the extra power and firststrike. Generally, the geist never goes into a fight he can't win, best case, he sees no blockers at all! ^^ But nice Idea, without the cryptics I would instantly add it!