Well, in my opinion, if you strip aikido from it's etiquette, protocol and dressing it wouldn't be aikido anymore, it wouldn't even qualify for a true budo.
Aikido is not a matter of personal definition but a complete martial art. There are people who are making convenient choices based on their personal opinions, so we have schools that practice no weapons because it seems useless, schools that don't adopt the proper etiquette, because they see no point in it but then these choices are showing badly on their technique.
You can make, serve and drink tea without performing the tea ceremony, it would taste the same. But you cannot call it "tea ceremony" anymore it would be mere "tea drinking". In the same manner you can practice kote gaeshi effectively without the etiquette or hakama. It can be a good disarming technique and combat method. But it wouldn't be a martial art anymore.
Studying the culture of any country by reading books is a very different thing from practicing a martial art as a way of life. Stripping it from any of it's core elements out of convenience would only leave your practice poorer...
Morihei Ueshiba, of course, changed all kinds of things - including etiquette, protocol and dressing, and it still seems to have remained budo. For that matter, if you can't change things without Aikido dissapearing then it has already dissapeared, because nobody, not even the Iwama folks, trains just the same way that Morihei Ueshiba did.
All budo, for that matter has changed, and continues to change, over time. People don't wear quite what they used to wear, they don't behave quite the way that they used to behave. Things move on.
Practicing a martial art as a way of life has very little, IMO, to do with funny clothes that people didn't even wear 100 years ago anyway.