The prevailing western take regarding isometrics, like dynamic resistance training, is to focus on specific muscle groups, which is opposite of the IP/IS training, i.e. whole-body, approach without expressly engaging muscles.
This is factually incorrect and I wish people with little or no exposure to modern strength and conditioning would stop talking about it until they earn an opinion the way everyone else has to: with a couple years on some rings or under a barbell.
Olympic weightlifting, powerlifting, bodyweight conditioning, gymnastics, swimming, cycling, rowing, and jumping rope are all multi-articulate movements that use as much of the body as possible, as intelligently as possible to accomplish tasks.
The much ridiculed discipline of bodybuilding is the *only* area of "western" training that isolates specific muscle groups, and you have trotted it out as a straw man with which to knock down a huge range of disciplines backed by success records going back in some cases thousands of years.
To my knowledge no one has ever suggested bodybuilding as a path to developing martial arts skills, much less as an alternative to internal skills. Few athletes other than bodybuilders even considers it a fitness methodology because of a long track record of poor skill transfer to other activities, a drawback that is widely assumed by everyone else in fitness to be the curse of training muscles in isolation.
Note I am not implying that any of those disciplines will serve you better than internal training in developing Aikido skills, I am merely trying to clear up the factual errors being presented.