After googling about the ELAN microelectronics corp, I came across the following patchset submitted to the Linux kernel:

https://lwn.net/Articles/496137/
It turned out that the touchpad I2C interface is used as a I2C - HID interface. It is in the vanilia mainline now, so it seems to be a good starting point. Basically I will need to create an I2C - HID - BLE - HID converter.

I have also rerouted the board to align the MIFA antenna to the proper direction:

Also made some paper printouts to verify the physical dimensions:

The BLE module footprint had some problems, but fixed now. The rest of the connector verification waits to my PID controlled flat iron because removing the FPC connectors will require preheating what I do not really have ATM.