I think it depends on what your focus is in your practice. But certainly the framework should be one that encourages proper body posture, structure, and provides feedback for progression. I think having a really, really good instructor is more important than anything else when it come to aikido.
My focus is on learning more about Aikido, become good at it, understand itīs various techniques better and how they should be applied, body posture, structure (what do you mean by structure ?
but also to try to integrate aikido into my everyday behaviour. I practise Aikido because I regard it as budo and selfdefence training, but I also see it as a personal journey where "masakatsu agatsu" is an important concept.
You mention a good teacher is the most important I agree so I also ask myself how Aikido teachers become good.. but thats maybe a different subject for a different thread.