Blending Constrained AR + Non-Constrained AR View Targets

When you blend between a camera that has Constrain Aspect Ratio enabled and one that has it disabled, the result is an interpolation of odd letterboxing where the black bars transition from left/right to top/bottom.

I understand that this is the result of AR calculation but I feel that this particular transition would never be desirable in any on-screen production. Is there a way to disable it while maintaining AR constraints of a single camera?