Are you sure you mean "outside the body"? When I spin a chair it usually rotates around an axis, not a point. So, do you mean center of mass, the intersection of the rotational axes or something else?
When you spin a chair or whatever you will find it has an axis around which it is turning, in fact I would relate this axis line to center line in Aikido. However, the center of that line is of course one point.
Let's take a ball. If you spin it you will see what you have just described. Now see the ball spinning say vertically or from north to south and you will find the axis is now horizontal. As you change the direction of the spin the axis changes accordingly but there is one point which doesn't change at all and that is where all those axis meet and that is the center point.
So center is the point around which all things turn, from which energy goes out and comes in and turns around as I said earlier.
Throw a pebble in a pond and you will see the effect of this energy motion.
Now in Aikido I purposely get people to create a point outside the body in order to get them to see it is something they have to create, to do, to take responsibility for and not think it is just a physical thing. The body of course has it's own center but you have to put your spiritual center aligned with it and the body is most comfortable when you put it there rather than under your foot or in your pocket.
A foreward ukemi is indeed extending Ki and projecting and turning your body around center is it not? If you put one point inside your body and let energy go to it you will feel one feeling. Now put it just outside the body and let energy go to it and you will not only feel a different feeling but you will feel more enlivened and centered. So yes I do mean outside the body.