One last option. I have also been asked if it is worth cross-training separately in internal power. I see from discussions on aikiweb that some people are trying to develop this power outside the teaching model of aikido. Sometimes it's called aiki. Sometimes it's called something else. Morihei Ueshiba called the internal power in aikido kokyu ryoku - breath power. I know that because that's what he told both the teachers I trained closely with. They were his direct students. Anything that improves your budo is a good thing. And I can't judge the technical ability of people who are teaching this. But I'm not interested in negative opinions about aikido from people who don't do aikido. This concept of training separately in internal power is not really known in Japan. If you train sincerely in any martial art eventually you will develop inner power. I have met aikidoka, karateka, judoka and people who practice kobudo who have breathtaking inner power. And I have seen many more examples.
I can't speak for everybody who talks about this stuff, but Dan (for example) makes a very clear distinction between Aiki and Internal Power.
Morihei Ueshiba, of course, used both terms, and also appears to have made a distinction between the two.
Kokyu-ryoku as a term iteself has a long history in the martial arts, and the same term is used in Chinese internal martial arts, with the same meanings as Ueshiba, the connections to Internal Power. I touched on that slightly in this post
In the diagram in this article
you can see that the Sagawa line of Daito-ryu also uses the same term "kokyu-ryoku", which suggests strongly that Ueshiba's source for that term is Sokaku Takeda. Yoshimaru Keisetsu, at least, equates it directly to Chinese Internal Power,
If Kokyu-ryoku is Internal Power, and Ueshiba trained in Kokyu-ryoku, then I'm not sure how training in Internal Power qualifies as cross training, or in training something "outside" of Aikido.
As to negative comments - well, I can't count the number of times that I've heard direct students of O-Sensei make negative comments about other direct students of O-Sensei in open rooms, so those kind of things certainly aren't limited to those "outside" the Aikido community. IMO, in any case, deciding who, exactly, is "outside" the Aikido community can be kind of problematic.