Pierce the defense of the opponent? Last time I checked there was no Def stat in FFT, and as far as I know Charge doesn't help you get around their evade at all.

As for Summons, sure you can lock the Summon on your enemy, but if he gets to move before the summon goes off, your Summoner will be 4 panels away, and take 1.5x damage, an insta-kill from most monsters.