I was that conjurer of the previous thread:
viewtopic.php?t=3440&highlight=alcoholic+iced+teaI'd imagine you'd need a fair amount Maltodextrin for sweetness and just a lot of tea to make the brew strong enough. I suggest you just give it a go, maybe only to 5L, so it's no great loss if it ends up tasting shithouse. Try several strains of tea, i.e. chamomile, lemon, rhubarb, rose hip ect... Also don't forget the Dextrose to give the brew some alcohol. Honey would also probably go down well in the brew.
But this method will require a lot of trial and error over several brews, and I've got to say I don't want my primary being used up for that long.
For now, I'm with Chris, go the Vodka/Contreau!
If you're keen, by all means give it a try...