Click-to-hold is one of the features I really miss from HS and it's unfortunate that it's gonna be a bit tougher to implement for now.
left-click on a card to play it
I'm assuming this wouldn't be a default setting? Seems kinda risky to assign a one-click action to play a card as it might lead to missclicks dropping a unit with no confirmation?
The other actions seem top notch!