Sorry for bumping an old thread.
I'll start by saying I don't know how Time Units are measured. I think this question needs answering--> How do X-COM operatives open doors if they're carrying a two-handed weapon or even if they're carrying a pistol, what about a door that might possibly be locked anytime anywhere? Yes, all doors in the game just open for you anytime(even garage doors and UFO doors), so I can definitely see an operative kicking a door open every time, because it's an aggressive way to get a door opened quick and without needing worry if it's locked or unlocked.
I'm just speculating here. If X-COM operatives kick a door open, it would also consume some energy too. Also I think since UFO doors have a slider sound, then lets just say UFO doors open automatically for you because it has a sensor that detects movement. It shouldn't cost any TUs.
Kicking closed doors open should be standard procedure.
So here's a suggestion: Change the sound of a door opening normally to a sound of BAM! A door getting kicked open! Now that's being assertive! How about it?