Better FX keyframe interpolations mode

There might be a way to improve all the FX interpolation type.

I take the elastic for example (but it's the same for other).
The problem I see is that the interpolation type is attached to the start key (prior to the elastic movement itself) condamning access to the out tangent (see screenshot).
You have to add one more bezier keyframe to make the movement as you expect. Note that the following keyframe is catching the end of the oscillation.

I have an example that, I think, works better and more artist friendly.
It's the spring effect of Duik (open source toolset for After-effects made by Nicolas Dufresne ) :

The key that hold the elastic interpolation is the end key.
The start key is a normal bezier (or anything else) and the end key catch the final position before the momentum make the follow through oscillation and pull back (and then return to final position). This way the artist keep control of the start of the movement and adjust the end.
The chaining of the movements are achieved without tweaking other keyframes.
There are approximately the same values settings : Elasticity (correspond to Amplitude) and Damping (correspond more or less to Period).
Interesting thing : if you put damping down to 0, the object oscillate indefinitely from it's first momentum.

I know that at the root of the animation system it's not the same principle but it might pop some ideas in the heads of some devs people.

Maybe we will get this working without relying on keyframe interpolation at all with the rigid-body bones proposal I saw previously ;)

Blend well fellow blenders