on both points for Aikido, not going against the joint and attitude, Kisshomaru Ueshiba and Koichi Tohei are in complete aggreement.
Maybe it's not shared by every "aikidoka", but that these two men agree
on this perhaps should make those who practice aikido consider how they
practice and what their goals are in practice.
And the fact that other "students turned teachers" of the founder of Aikido (just like in the above case of K. Tohei and K. Ueshiba) may agree
that going against the joint is part of the technical repertoire of Aikido "this perhaps should make those who practice aikido consider how they practice and what their goals are in practice"
Of course another question is whose technical model do we want to take for a definition of "Aikido"tm and then at what point during the person's training/teaching do we want to use as the example of what constitutes "Aikido"tm technique.
Imho there is no better example or definition of what Aikido "is" or "is not" other than its Founder. I mean, he is the one who did the defining of the philosophical and technical basis of the art to begin with. Everyone else learned what he taught and put their own spin on things based on personal perceptions, previous training and realities. I don't think the "observer effect" can be totally removed from any sort of transmission system that involves the passing on of physical movements and thinking, as we all do so in slightly different ways whether we realise or not.
As such, what K. Ueshiba and K. Tohei may show (or agree on) regarding "what is Aikido" and what folks like R. Shirata, G. Shioda, M. Mochizuki or K. Tomiki may agree on as "what is Aikido" based on what they personally experienced to be "Aikido"tm as shown by the Founder at the point in his life that they trained, will both be correct as far as these students are concerned, but will both be very different in expression in many ways as well from each other.
Before we can go labelling what is and is not Aikido we have to precisely define Aikido. Not "our" Aikido, but Aikido. If we see Aikido as a collection of principles and philosophies and not a collection of techniques, then "what is Aikido" becomes a concept of much speculation and interpretation based on the principles it claims to adhere to.
Since Aikido had evolved from Jujutsu (of which Judo is another evolution) there are students of Ueshiba M. who placed the technical repertoire of Aikido precisely within a certain sector in the scheme of all Jujutsu techniques which consisted of Nage, Katame, Kansetsu and Atemi Waza as we can see here - http://homepage2.nifty.com/shodokan/en/kyogi4.html
. In this categorisation, there are joint techniques that go "against" the movement of the joint.
As far as "legitimate paths" go, well it all depends on where you sit imo.