Yeah, XCOM 2 is sapping my productivity at the moment, but I think it is a net gain in inspiration and motivation.
Flying units is something you can do in a number of different ways, and I cannot think of a good “standard” implementation that would work for any game. Multi-level grids certainly opens up new possibilities for implementing flying units, but it all depends on what you have in mind. It is certainly possible to have invisible grid cells above ground that only become selectable when you have selected a flying unit, if that is what you are considering. I think such a feature might quickly become confusing to players, though, so you would have to think hard on the best way add this.
The update is indeed not out yet. I sent it to Epic a long time ago, and though I am used to them being slow, I think there is another reason why they are being particularly slow in this case. I sent them my new update for UE4.10 at roughly the same time as I sent my UE4-11 Preview update, and I think this might have confused them into thinking I had only made the update for 4.11.
Since 4.11 is right around the corner I don’t think I will bother pushing Epic too hard on this. This way the 4.10 version will always be available for download, and because of the big changes I’ve made in my 1.5 version for how edges are implemented I think it will be useful for people who begun using the toolkit early to have a version with the old edge array system readily available. This means that my update will be out when UE4.11 is out, as Epic will have to update my toolkit in any case.