Hi Andie,
That is an interesting question you've brought up. What I must point out first of all though is that if you simply use the boiling water to thaw the fruit then the temperature of the fruit would be fairly constant at around 0 degrees celsius (32 farenheit) this is due to something called the 'latent heat of fusion.' What this means as it applies here is that unless you continue heating the fruit AFTER it has thawed (i.e. all the ice crystals within the fruit have melted), the temperature of the fruit will not get very high. You need to maintain a temperature in excess of about 50 degrees celsius (~122 F) in order to kill the yeasts - realistically a higher temperature would need to be used (many yeasts can survive for quite a while at relatively high temperatures).
If you are infact heating the fruit to perhaps 80 degrees celsius (176 F) or so, then I would think you could probably get away without using metabisulfite in the initial stage. Sulfur dioxide (as was pointed out above) primarily 'stuns' the wild yeast, hopefully long enough that your wine yeast can get a good head-start. Even though your must is 'unprotected' while it cools (before you add the wine yeast) any invasion of wild yeasts will still be on the backfoot against your more vigorous (and hopefully properly hydrated and prepared) wine yeast.
I hope this is of some use to you, I wish you the very best of luck,
Regards,
Michael