Yeah, I agree there is plenty of time to see what weapons are best, but just like the overheat button flashing thing, it is a user interface thing. Cohh, who is a prime example of what new players will do because he knows about what most players will know, makes mistakes like this. He constantly does it with overheating, switching off higher percentage weapons, and doing less optimal things because of a lack of understanding through a sub optimal UI. Other suggestions in other threads have said to enhance the overheat warning button which is another small user interface improvement over what we have now. If I took your argument to the overheat thing, you can say the heat bar and flashing text is enough, but a simple 50% box set at 50% opaque around the flashing text might draw the commanders eye towards it more because of simple contrast.
This weapon location interface is small potatoes on the front of it, but may help other users understand why things are the way they are based entirely on the user interface. I haven't seen anything in his streams where he realized that arm mounted weapons have a higher hit percentage, but a simple ARM/TORSO split would give one more clue of why one weapon is a higher percentage vs another, even though it is the same pilot, shooting from the same mech, at the same target.