Current shadows are quite ugly. Ogre has support for ESM and a sample that show how to use them. Study that.
This require changes on the way shader parameters are accessed by Annwvyn regarding the Ogre compositor. And the ESM sample isn't helping much.
Instead of copy-pasting a bunch of code from the sample, this will require some refactoring, alongside the exposure control code for HDR. Task rejected in 0.4 roadmap