Stormcast Scions of the Storm ability

[Ian R]

You can place one SCE unit in the Celestial Realm as a reserve for each unit you have set up on the battlefield.  Can that unit set up on the battlefield be an ally unit, not a SCE unit?   From a reading of the rule I think it is fine for the unit set up on the battlefield to be a non SCE unit do you agree?

[Nos]

It dosent say the unit on the table has to be Stormcast so don’t see why not 

[azoxystrobin]

Doesn't scions of the storm specify stormcast unit? Hang on, yes it does, it says, instead of placing a STORMCAST ETERNAL unit on the table, you can instead place it azyr as a reserve unit.
So obviously an allied unit can't be placed in azyr.

But can an allied unit be placed on the table to count for that 1 unit on the floor before putting a stormcast unit in the sky?
I suppose so, indeed the rule doesn't specify it has to be a stormcast unit.

[Isotop]

Units "on the ground" may be allies, since Scions of the Storm does not specify STORMCAST here. 

Another interesting point for you guys:

It seems you do not even have to "alternate" (if you know what I mean)  between units "on the ground" and "in the skies" - as long as you have at least as many units "on the ground" as "in the skies" at the end of your deployment.

Feel free to discuss.