Ok, so I might not grasp exactly what you’re after but here’s what I can offer…
It’s not clear to me that if a level sequencer has control of a camera that you will be able to allow a player to control it simultaneously…seems like they’ll be fighting each other. With that being said, you can change the camera of the player controller by using SetViewTargetWithBlend node. Once the PC has control of the camera it can rotate it around without issue. Here’s a good example of that HTF do I? Change Cameras in Unreal Engine 4 Blueprints - YouTube
Like I said, it’s unclear to me that you will be able to grab control of a camera which is being managed by a level sequencer. Let me know if it works out though.
EDIT: I wonder, if you only let the level sequencer touch the camera location (not full transform which includes rotation and scale), then maybe the PC will be able to change the rotation without fighting the sequencer…sounds like a fun experiment.