I'm super positive Mitch had a solution to this issue, something we may have all overlooked.
I can only say be patient and what for the TO to make a ruling in the next day or so?
According to Mitch's tournament thread he already has made a ruling - spells will be able to be cast multiple times so long as they meet the casting value (so dispelling wont stop multi-cast).
However its still good to hash this out between ourselves. Never know when we will need to come to a consensus on the issue.
EDIT: Even though he says that spells can be multi-cast in the thread, Mitch mentions that he will add the question in the FAQ. I imagine that he needs to speak to Todd from GW Perth first before making a ruling (as I believe this event is being run by the both of them).