Help Wanted Animate 5 fingers individually and combinable

Hey guys,
I'm searching for an best practice advice here. My game will feature a hand with 5 fingers. Each indvidual finger should be able to transition between stretched out from the hand to being contracted (if that's the right word).
Which setup works best for setting up an animator that can precisely control each individual finger from script? If of any relevance: Using Blender as a modelling software (so I cannot use Inverse Kinematics, from what I have read).

This is what I would like to achieve:

 

In case anyone searching this at a later point.
The keyword is BlendShapes. I created Blendshapes for every unique finger in default and stretched Position and blend them using Scripting. This is however only good for rather simple SetUps (2 States, rather simple transition)