Here's a QoL / time saving idea I've been kicking around. I'm pretty knowledgeable myself when it comes to writing software, so it might be something I take a stab at if folks think it could help.
Basically when pressing ALT, in addition to showing facing, also draw a small bubble above each of your soldiers, which shows approximate remaining TUs. My mock-up below shows what I mean. The color coding should be something like green: >=50% TUs, Yellow 4-49% TUs, Red < 4 TUs (basically no time to do any movement). The bubble should also be partially filled based on remaining TUs (e.g. a half bubble means 50% TUs)
I think it can really help save time if you're looking for a soldier with TUs to fire at an enemy without resorting to clicking on each of them.
Bonus: when holding ALT, also show the TU bubbles of off-screen soldiers on the edges of the screen. This can help you when you're checking to see if anyone still has TUs remaining before the end of the turn.