I was hoping you wouldn't ask me that, because I have to use my brain, and lay back in my chair, drink my second can of beer and think:
Calculation of tangent is easy, and requires one calculation per line - tan@= x/y or whatever - and you look up in tables, arrive at @ and can set the A axis at the right angle. A little bit more in it, depending on + or - but essentially a one off operation per line.
CV is much more complicated - since, depending on the setting when CV is to start, and depending on the acceleration settings for your axis, then (because this is in the slowing area of one line, and the acceleration of another) :-
1. You have to calculate where the XY poisiton of the old line would be, in line with the deceleration rates set.
2. You have to calculate where the XY of the new line would be in relation to the acceleration rates set and the times of the introduction of the CV.
3. Combine the two into a new XY position.
4. Save the where are we now position and then calculate the speeds necessary to move the axis to the new position.
5. Implement those speeds.
6. Do this again immediately because the situation is always changing.
What you are then asking is do another calculation of new x - old x, new y - old y, = x(t) and y(t). Then do the tan@ -= x(t)/y(t) again and then ook up a new tangent angle for the A axis.
I suppose it can be done - but whether it will be inside the parameters of our bog standard P.C. to do it in the near future, or whether you will have to add Smmooth Steppers amd an add on maths cards in the computer, I wouldn't like to say.