I dont know how the FL xenon leveling works but the MINI xenons work from information received from a level sensing switch and linkage on the cars rear axle.
If the leveling is all done within the light unit on the FL great but how do you tie that into the manual system, or is it just skipped out somehow so that control does nothing?

The software exists in all cars regardless if it was factory fitted with HID.
When you activate via CCF the system senses HID unit connected and the software activates the actuators in the assembly itself. The FL2 has suspension sensors on each corner so the sensor system already exists. Without looking over the schematic I would logically guess this is what the software looks at aswell as some sort of level sensor.
Your manual leveller I imagine would not work once you've told the car that HID units are fitted.
I've not looked specifically at the electrical schematic but from a manufacturing point of view it's possibly a swap and edit job. The only thing you need to check if there's a HID headlight module which sofar I've never seen in my search's on Topix. MY15
Tyre Pressure Monitoring System (TPMS)
Surround Camera System
InControl Apps soon to be replaced with CarPlay (WIP)
Meridian Premium Surround Sound
Digital Audio Broadcast
Timed Climate
Cruise ECO Data
Follow Me Home Reverse
Extra Features Menu
Picture In Motion
4x4i screen (WIP)
Digital Broadcast TV
Meridian Rear Media with WIFI
Factory Powered Tailgate
Blind Spot Monitoring (BSM)
Reverse Cross Traffic Alert (RCTA)
Electrochromatic Wing Mirrors (WIP)

oh my I go offline for a day and all these questions lol
my units are factory items so still have the level function etc working, all I had to do was have the car enabled otherwise they flicker.
The units I have are actually the dynamic ones which turn with the steering but you need this to be already fitted on the car to work and its really not practical to retro fit.
Anyway sorry I posted the ebay link I genuinely thought it was better than putting up a for sale post my bad.

For the record, the location of the module responsible for "Self Leveling" is in the plenum chamber, callout 13C788. Someone with a halogen equipped vehicle would need to verify if the harness, for the module, is present in a non HID equipped vehicle.
Swivel Action is purely and CCF acvtivation. There is 2 field, one for activation and another for increase/decrease swivel action on early HID units.
You'd also need to verify the wiring/sensors for levelling on both front and rear suspension arms.

 MY15
Tyre Pressure Monitoring System (TPMS)
Surround Camera System
InControl Apps soon to be replaced with CarPlay (WIP)
Meridian Premium Surround Sound
Digital Audio Broadcast
Timed Climate
Cruise ECO Data
Follow Me Home Reverse
Extra Features Menu
Picture In Motion
4x4i screen (WIP)
Digital Broadcast TV
Meridian Rear Media with WIFI
Factory Powered Tailgate
Blind Spot Monitoring (BSM)
Reverse Cross Traffic Alert (RCTA)
Electrochromatic Wing Mirrors (WIP)