I managed to create my mvc treePanel by overwriting a initComponent function on the view, just like vollchraZ said. I also needed to specify a root config on this treePanel view (root: {},).

This is a minimal tree-MVC working example i created:
mvc-tree-example.zip
To make it work, just change the paths of extjs files in index.html to your existing paths.

(check the view/FileTree.js)