The command system for your wingmates in the games was pretty basic. They weren't based on the Numpad as far as I can remember, they were Shift + [insert key] commands, like Shift + A to tell your wingman to attack your target, etc.
Used with the Z key (introduced in TIE Fighter) to see what your enemy was doing, it worked pretty well. I
think, but can't remember, that X-Wing Alliance improved this by putting all the information on the 'Z' screen on your main targeting screen instead, so you didn't need to leave the cockpit for any reason.
Based on one or two lines of dialogue, and not in the context of actual combat (it's mentioned only when they pass through the death star's magnetic field, when they're not actually fighting).
As noted, it's mentioned more than once, and in combat as well. It is obviously important to SW space combat.
And in X-Wing there was only one tactically sensible option anyway, full charge all around with energy pumped into them from your lasers. Having lots of different apparent options when none of them are any good so you always do the one same thing is not depth, it's a whole chunk of fiddly crap that can be completely excised without affecting the player experience in any way at all. It's a darling that needs to be murdered before you can start producing space shooty games again.
That's just flat untrue. There are
plenty of times in the games where, for example, you're pursuing a target in front of you or something and you're under heavy fire from behind and you just don't have the time to turn around and take out your attackers - putting the deflectors to double-back so that your weakened arc goes to the front keeps you alive. It's a cool mechanic, it's part of SW space combat, it should stay.
A really obvious one is strafing capital ships - deflectors double front whilst strafing, turn around and fly away, deflectors double back. Did it all the time.
As for laser single/ dual fire, this was also useful - you use single fire for long range work so you can adjust your fire as the enemy approaches easier, and quad or dual fire close-in where it's more important to get one big hit.