Well, it's obvious that a boxer may use quick, non committed jabs and an attacker with a knife will probably use fast small moves instead of a full step from a distance.
But, imagine that you have a beginner in the dojo and all of a sudden you just jab him fast. And you repeat that in every attack.
Not only he is gonna get badly...bruised but also, and that's the worst, he will never learn anything. You can't start teaching a six year old how to write by asking him to write an essay on the greatest authors of english literature on his first day at school.
But after a level when he has learned the basics the attacks must become, gradually more and more demanding and this is the way we train, we use the basics and also we use attacks like a close fast jab with the front hand with no step at all.
I know the majority of the dojos neglect that and give a wrong impression, but that does not reflect the true effectiveness of aikido as a martial art, only their own, personal level of effectiveness...
See the thing is, if you want to try to figure out how to "make your Aikido work against" proper boxing techniques, you need to learn how to box properly. Right? Or else you won't be giving good combinations of jabs, crosses, uppers, hooks, what have you. You'll wind up with a new set of attacks that still don't look to an actual boxer like real attacks.
In order to begin to figure out how to apply the principals of Aikido on this new field, you need to learn the principals of pugilism yourself.
So how much of your Aikido training time should you spend doing that? That's always my question when people start talking about the attacks as though they are singular physical events as performed by a robot on an assembly line. We've all got a finite amount of time to train, even if we're full-time students. How much Aikido training time do you spend practicing in a different martial context (or non-martial context, as the solo training people do) in order to develop some level of understanding of that context, so you can then begin to figure out how Aikido is supposed to work over there?
For boxing that's going to be heavy bag and speed bag work, hitting striking pads with a trainer, various types of conditioning, and lots and lots of sparring. For knife fighting that is going to require hours and hours of learning techniques (often similar to Aikido fwiw) and running through continuous flow drills. So how much time is left for Aikido, and what happens when you realize you like boxing or escrima better?
I tend to think that the most reasonable answer to these questions involves taking some generalized, standard attack vectors and sticking with those. Get new students familiar with them and then build intensity...I am not sure increasing complexity or sophistication of the attacks is worth the effort.