There is no confirmed working LookPilot setup for MechWarrior 5: Mercenaries yet.
What to try (general methods): the Connect to Any Game guide covers the three routes - freetrack (TrackIR emulation, works only if the game supports TrackIR), virtual joystick (for games with joystick camera input), and mouse emulation via opentrack (for mouse-look-only games).
If you get MechWarrior 5: Mercenaries working, please share your setup on our Discord or open an issue on the docs repository - it will become this guide.