How to automate generation of artifacts from custom persistence models?

I have developed my own language, custom persistence module (XML) and generator. As part of Maven build (being run in TeamCity) we need to:

1. Load XML file using my custom persistence module
2. Feed loaded model to generator and store produced artifacts somewhere

Existing mps-maven-plugin (http://jetbrains.github.io/mps-maven-plugin/) accepts models in MPS native format only (*.mps). 

Build language doesn't allow to execute workflow steps (load model, run generator).

Any guidance is very welcome!