Would it make more sense to just have continuous fire on by default and make the right-click a ceasefire instead? Just a thought I had while reading through your stuff.
Viewing post in Rise of the Trash Panda: Dev Blog
I messed with it a bit more and I cracked it. It feels really intuitive now. You hold the left mouse to constantly fire bullets, you right click to select the secondary action card, while still firing bullets, and you release the left mouse button to activate the chosen card. you can also activate the card by pressing the left mouse button while it is highlighted. It's subtle but it made a big difference.