Daemon Rules Update

Ok, so they haven't updated the rules with an FAQ, but while I was looking on their website I did notice that Flamers of Tzeentch are indeed a special choice. I guess this counts as a confirmation to that question.
That said, for a Tzeentch themed army that leaves the whole rare slot without a Tzeentch unit. I guess you could use a Soul Grinder to fill that spot, or even use rules for a Beast of Nurgle and just make it a Tzeentch daemon that 'count's as'. Still, for a basic 2,000pts list there is enough Tzeentch daemons to easily fill it without needing those rare slots.

Up-date (5/9/12): There is one type that could be a substitute in replacing the Beast of Nurgle / Fiend of Slaanesh. Called the Firewyrm of Tzeentch, it was a type of Chaos Spawn in Warhammer Online.

Tyranids would give some parts for a conversion.