There has been a few suggestions talking about mesh distortion in the timeline, this is a common feature in other animation software and would be very powerful.
But sadly there is one big concern, that needs to be adressed, before adding it to the timeline would even make sense to me.
Construct currently draws tris instead of quads
this leads to the texture looking off in a lot of cases, this is very undesirable as the usage of mesh deformation in the timeline would mostly be for visuals. (even the advertised examples by construct for using mesh don't work well for that reason, unless you want your textures to look terrible.)
This problem would be fixed if the drawQuads method would be used instead
Example to visualize the problem, if it's still not clear I can add more examples.
You might argue, just add more points, but this would be bad for performance as well as would make it insanely difficult to edit and place the points.
If tris need to stay we would need a way to add edges to the mesh in user defined placed (look at spine) so we have control over where the edges are and with it where the mesh should bend. Currently we can only place them in a perfect grid.
http://de.esotericsoftware.com/spine-meshes
But for transforming a grid quads are the better solution.