Tzeentch Changehost endless spell swapping question

[Lord Krungharr]

Looks like I can run a Changehost using my smattering of Tzeentch Daemons, as the Burning Chariots count as battleline with my Herald on Chariot as general; makes a single deployment drop army.

If I redeploy the Changeling, cast the Purple Sun, then Changehost swap him with another Herald or Lord of Change, have that one cast and endless spell too, can I then swap a second time since I'll still have 9 models in the Changehost?

Changehost says while the battalion still has 9 models I can pick two different pairs of models to swap.  It doesn't say any particular moment in the Hero Phase though, so my thoughts are at least the two endless spells could be cast amidst the enemy lines like that.....but does the second pair of models count as different if only one of the models is different?  First swap pair is Changeling/Lord of Change/, second swap/pair probably Lord of Change/Herald on Foot.

Anyone have thoughts or experience with this?

[Dreadmund]

The errata changed the description of changehost from the book to be "At the start of the hero phase". So no, you can't do that, because spell casting happens after changehost swaps occur.