Not strictly true. You can preempt their attack when you think you are in danger/trouble while they are busy shouting/posturing/sqauring up, whatever.
You are going to instantly know what attack they will perform are you? What, do you have the gift of the force master Jedi? No man can see the future and a fighter who knows nothing knows nothing of posture and so cannot embrace one. One cannot stand in aiki-posture or Kami if they do not know what it is- if anything the aikidoka will lose the edge as they WILL be trying to establish posture....
i have two arms and two legs- which will i use?
How will i use them? round and hook or perhaps the direct strike. But then again you could always go with the uppercut- or even the down cut...
Oh-how about elbows and knees to really do damage- then again i could stay distant, using fast long ranged strikes.
Grappling- didn't think of that, perhaps a sort of rugby tackle- jumping kicks or flying fists. Head butt- there's a goodun.
as i said before- you know not what the enemy will do, as aikido is purely defensive (ref Shihan of the UKA or even Saito sensei) i fail to see how a defender can take the initial initiative of combat- Aikidoka can counter and throw/ lock- but they must fight to the enemies pace and game. They are the ones that determine the speed, they are the ones that dictate the technique, they are the ones that are coming in first.
That's my view on the topic.....