I'm working on this plugin whenever i have free time to do so, but as the tiny tank demo proves a lot can already be done with it. You could very much make a quake style fps as things are now, although you'll have to program simple 3D collision detection yourself. Tiny Tank has 3D physics/collisions which were made using events so an fps should be very easy in comparison. Animation will likely come in the future, but again I update at the pace that i can. Read up on 3D collision detection, sphere-sphere collisions are incredibly easy to implement:
http://studiofreya.com/3d-math-and-phys ... -response/
The plugin is taking a long time because it implements more complicated collision primitives and uses a spatial hashing scheme to accelerate things, but for simple 3D collisions like you'd need for DOOM sphere-sphere aswell as constructs collision system should be very useful
Also, obtaining mouse coordinates in the 3D space is based on your camera position, field of view and your window size, as well as the plane you wish to project onto, it's not something that the plugin can't do, its something you must use math specific to your requirements to solve.