I mean, it probably comes down to fundamentally changing how the camera setup is TBH (cause control rotation be weird with this setup currenlty). There are different approaches to make a FPS cam: Have 1st and 3rd person mesh approach, or the TrueFPS route which the camera prolly needs to be attached to the head bone and adjustments that way too.
At the end of the day, A lotta people want to mod it to do different game types (ARPG, FPS, etc.) … but it seems it’s a bit in discovery mode to understand how to approach different funamentals with doing so. It’s a top down approach to visualizing it (starting with each LyraExperienceDefinition and seeing all of the asset stuff from there). Would love to see a more… comprehensive breakdown on the Setup and engineering side more 
. But, for starters, I guess one coulllddd make a child of LyraCameraMode to see if they can adjust it to make that work accordingly for the FPS camera