I did check out custom property constraints and while they're quite useful, i'm afraid they aren't what i'm looking for right now.
I'll try to explain what i'm trying to do with an example:
Let's say i'm creating an animation which currently only has 2 keyframes, i'd want to be able to change how i transition between the first keyframe and the second. If i had only one property, then in the editor i'd only see one curve.
However, once i'm animating multiple propeties, i'll see something like this:
Where i have multiple curves instead of one.
If i select multiple nodes at once and try to edit them, i'll instead only edit one of them:
Or in other words, i'd like to map a single curve to all propeties at once.
The script i shared above interpolates between an animation using a curve, where value 0 represents the start of the animation and value 1 represents the end of the animation.
The advantage is being able to quickly create unrefined animations for prototyping purposes and, once refined, it's then possible to create new variations only by changing the keyframes.
Unfortunately, having to change how quickly an animation is played through a script makes it much harder to take full advantage of unity's mecanim state machine.
Being able to change how tangents are calculated for multiple propeties at once does help, but it's not the ideal solution.
An "already done" example of what i'm trying to accomplish can be seen in overgrowth, where characters are animated using just a handful of keyframes with different types of interpolation. The developers made a GDC video session that can be found on youtube and i was trying to mimic the same approach. :)