Custom projection matrix on virtual camera?

Is it possible to set a custom projection matrix for just one virtual camera, and have it blend with the default projection matrix for another camera? Or is there a way I can do something like this myself while still using cinemachine?

 

I have two cameras in the scene, one top down and one third person, that the player can switch between. For the top-down camera, I want to do an oblique projection and possibly some lens tilt.

So what I'd love to do, was be able to just set up the projection matrix on the top-down camera, and let cinemachine handle the blend between top-down and third person.

In an ideal world, cinemachine would support this out of the box in the lens settings of each camera, by exposing tilt and shift parameters (like for a real-world tilt-shift lens).

 

Ah okay, then at least I get lens shift which might be enough. I see I can also get the active blend from the cinemachine brain, which I might be able to use if I need to do my own blends of the camera matrix.