I know this is old. But I have to say this.
So mote it be, is a phrase used to confrim your wishes/intentions to the goddess.
When finished casting a circle, you say "so mote it be" to confrim the goddess' presence as you preform your ritual.
That the end of a spell you might say "this is my will, so mote it be" thus confirming to the Godess that you are serious.
But if so mote it be sounds weird to you. You can say
So shall it be or so must it be.