Modify mesh on load

Is there possibility to modify mesh, like uvs or vertices, during loading from fbx file? Im looking for something like XNA Content Pipeline, where you were able to put your own script to modify a little bit original model (geometry etc).

I know there is something like MeshFilter, but I believe it is not best solution in terms of performance.

It is possible to load a model into a scene then modify it and Save the changes.

Look at Procedural examples on Unity Asset store and also this thread

http://answers.unity3d.com/questions/39311/editor-scripting-how-to-save-a-script-generated-me.html