Welcome to the forums, first off
As someone who maybe new to eldar, but has had a couple of games, and some close ones against powerful books at the moment - I maybe able to offer some insight.
It's an interesting list - certainly don't see many like them. I have, however, used Children of the Open Skies, and have found as it useful as hoping it will be!
First off, can spiritseers take from the Runes of Battle? I thought they just had runes of fortune, but I maybe wrong - never really checked. Maybe instead of quicken and restrain, however, there are some GOOD
runes of fortune powers you may find more advantageous.
There are two, specifically, one that adds 2" to charge rolls for a unit, and another that turns off an enemy unit from being affected by all auras - which can absolutely turn nightmare units into crystalline dust.
Children of Morai-Heg is good!
Honestly, I would almost recommend dropping a unit of Shining Spears, and adding in a full unit of 10 Howling banshees. Why, you ask? Because they have advance + charge built into their profile. Open skies give them 9" run, then you can command point advance if you don't roll a six, then use that rune of fortune spell to add 2 to their charge... then charge.
Last week I attempted this and literally made a 24" move, advance, and charge into a supped up unit of Admech Rangers, and wiped the unit before the Exarch even was able to strike.
Or, you could drop the wraithblades and add those howling banshees in addition to another full unit of aspect warriors somewhere. Maybe swooping hawks like you mentioned. I like the idea of the guardian defenders, Storm Guardians may also be a good alternative if you find your defenders incidentally rushing into enemy-favored combat situations. That way you can at least try to be aggressive and get some first strikes in.
As for the relic - sunstorm, always sunstorm. Objective secured on an HQ is huge!
I don't know about giving the spirit seer Faolchu's wing, because he'll always probably be slogging it with the wraithblades anyway.
Support weapons and war walkers, look good, enough to make the Astra Militarum envious.
Let me know if you have any questions!