Great video. This should be viewed alongside the article on Bombad Tactics on the Shifting Priorities "heat map" with regards to strategically placing your characters for the specific struggles and in general for most games. Good stuff!
Wait, you can only change stance at the end of the activation? I thought you did it at the start? Specifically, P12 of the core rule book says you may flip at any time
With a primary that has a larger base (Grevious so far) do you still split the middle or do you tend to hedge to one side or the other since you have a bit more wiggle room?
it really depends on what supports your taking. If its B1/B2 - you have plenty of wiggle room so doesn't really matter. If they are Magnaguard then you definitely need to be a little more central.
You are technically free to deploy however you like, but right now there is really only one optimal was to deploy. This will change however once we get additional Map Packs in the not too distant future.
If I am building a table I like to put some impassible terrain on those positions that the primary characters should deploy to. I find it then forces a little more thought as to how you deploy.