Kobayashi, Sensei, used to say that those who wanted to drop "ki" from Aikido, should be honest and call their art "Aido".
Having taught acupressure for the past 22 years, and having read one or two things on "ki" in that time, a couple salient points need to be considered.
1) There is an abstruse philosophy of Ki which developed first in China then later in Japan. This philosophy was derived in part from observation of how the body seemed to work, but mostly, it was derived from Daoism. As the discussion "progressed" the original basic understandings became increasingly esoteric, until the philosophy of "ki" was for the most part incomprehensible.
2) The part which remained focused in attempting how to understand how the human organismic body worked, however, was based upon empirical observation. Now the conclusions drawn are often faulted as being "unscientific", but the general observation remained true. Ki in this understanding is more concrete and directly related to how well the body functions. The understanding here need not be any more complicated than feeling "energetic" or "drained of energy".
When these concepts moved into the martial arts, their original introduction was based in breathing properly for the situation. In this manner extending one's awareness became a practical matter of survival. This is something which can be practiced.
There is an excellent book by Yuasa on the Body, Ki, & Spirituality (something like that) which has a very solid discussion of all these issues. I highly recommend it to you.
Suffice it to say, those who over emphasize the esotericism of the philosophy of ki and those who deny that ki has any reality or is even a part of Aikido, both are of the extremes. Practice and training is based in Chudo, the Middle Path. The extremes are interesting for discussions, but training is not a discussion.
Ki is the central character of Ai Ki Do, it cannot be excluded. Neither is it preeminent. Take a deep breath and exhale. Repeat frequently every day for the rest of your life. This is proper use of ki.