Bernd asked me in a recent post what the difference was between ki and intent and I sorta blew off the question by saying it was just different vocabulary for the same thing.
Intent, as I seem to be practicing with it these days, is about where you put your focus. It tends to be linear, and runs in whatever direction I choose. So I might have intent shooting down out my elbows or knees, or I might use intent to expand in 6 directions, or I might use intent to get under and unbalance my partner, as Hunter talks about in another thread.
The classic image for ki is breath or water. So ki flows in channels. Doing breathing exercises, ki connects palms and soles to center, and the practice builds channels which I can then use during waza. So when I use ki during, say, tenchinage, I'm opening but also connecting palms to center by extending ki along those channels--but it's an extension of intent, not a physical extension. Ki can also cycle within the body creating suppressing or lifting force on uke.
So similar, but not really exactly the same as I think about them. But whether this matters in any practical sense, I'm not qualified to say.
A little background first: "Mind provides intent, body provides mechanics. Spirit provides the interface whereby mind and body may work in harmonious synergy, blending their efforts, subsuming their individuality and realizing the state of mind/body. Spirit endows the mind/body unit with cohesiveness and structure. Spiritual power, in this case, is not measured in terms of the ability to perform work. Rather spiritual power is expressed by the strength of the mind/body unit." - from my blog, post 204.
The reason I bring this up is because intent belongs to the hidden realm of mind. The generation of intent is a mental process, the realization of intent is feeling. Intent is manipulated in order to achieve goals as you state above: "So I might have intent shooting down out my elbows or knees, or I might use intent to expand in 6 directions, or I might use intent to get under and unbalance my partner..." Intent is a tool that can be used to exploit the power of a coordinated mind and body.
I view Ki as something else entirely.
"To truly implement the Art of Peace, you must be able to sport freely in the manifest, hidden and divine realms" -- M. Ueshiba.
Ueshiba's three realms correspond to three aspects of being as follows: Body -- Manifest, Mind -- Hidden, Spirit -- Divine. Each aspect of being is associated with a process: Body -- Physical, Mind -- Mental, Spirit -- Connection. Each aspect of being comes to the realization of: Body -- Technique, Mind -- Feeling, Spirit -- Universe. The realms, processes, realizations and relationships of mind, spirit and body may be distilled down to the single word -- Ki, as depicted in the diagram below.
When I am fully aware of all three aspects of being I have a high degree of coordination of mind and body. When I have a highly coordinated mind and body I am in my most dependable and strongest state and am able to use intent with great effect.
So, FWIW that's how I would explain the difference between intent and Ki.