Question Second pair of uvs in SpriteRenderer

We want to be able to use batching with spriteatlas with some wavy~ shader for terrain sprites. This has the problem that the uvs of the original sprite will be not be able to be used when calculating how much wave the portion of the sprite should have (as top parts move and bottom doesnt). Thereof we need a second pair of uvs that can be used for a second texture to define the wavyness so we don't have to modify the material itself. Any suggestion how to solve this in general is also appriciated.

Thank you.