Hi guys, thank you very much for the feedback, those are some really good points for consideration.
I'd not really thought of taking a Windrider Host, however I must admit I'm intrigued by the idea. My concern would be what to do with the Warlock - give him a singing spear and turbo boost him around the board to hunt isolated tanks?. He feels a bit of a tax, and I'd rather not expand the Conclave upward to justify the investment. If he is viable as a solo mischief maker then I could see it working. Regarding the Cloudstrike formation, I can see how it would offer a solid firebase alongside the deep strike capacity, but I'm probably going to steer clear just from a modelling standpoint.
Regarding the armies it may struggle against, I gather this is because of their capacity to field high toughness/mobility units that can close distance and engage in assault, thereby getting to the Achilles heel of the list - no real assault capability. My plan would be to maintain distance and pick away with Starcannons, however I can appreciate this is easier said than done, particularly with cover/shrouding and whatnot. Again, something for me to think about.
So the last big question is Ynnari vs Craftworld. My hope was that by keeping the Aspect Host fairly close together and using the Warhost of Ynnead rule, that they could inflict a lot of punishment - Dire Avengers/Fire Dragons shooting twice and whatnot. The mobility of Battle Focus is certainly more universal, however I like the idea of being able to play more aggressively, albeit with careful consideration. Perhaps the best idea would be to run it a few times under each configuration and see how it went, then report back.