Mdbt40 gpio control integration/addon

I have an adafruit BLE friend board lying around and i’d like to use the Nrf51-based mdbt40 module mounted on it to control some buttons (sun shade curtains buttons). The board already has DFU OTA bootloader and therefore i can load .hex files from the phone, but i have access to stlink/v2 programmer if needed.

The Adafruit board does not have free GPIO but from schematics you can see they tied some resistors and leds to GPIO and desoldering the resistors would give you access to GPIO from the board, also soldering directly to mdbt40 module pads is an option since pads expose most of the available GPIO.
As to what software to flash to control the pins, so far i have found the following options:

  1. nrf sdk tools and OTA firmware update (hardest choice since it requires real programming skills)
  2. arduino-based code via NRF5 board board on arduino IDE, then somehow control GPIO through BLE
  3. web based control can be exerted from Nrf51 IO control

Now coming to Home Assistant side, i am running HA Hassio on a pi3 b+, i have no idea how to approach BLE gpio control. So far the 3rd option looks the most out of the box solution and it looks like i’d just have to create a dashboard with buttons that sends the commands through, but i have only recently started tinkering with HA so i am not very practical in dashboard and templates building.
Looking forward to this community suggestions on how to approach this. My programming skills are not that advanced since i’m self taught, but i can work with arduino code given some time.

P.S. all of this to spare myself from buying an RFLink to control a somfy RTS device, since i already own a broadlink rm4 pro. I have a pratic remote, and with an oscilloscope i found out all signals from the buttons go to the (only) onboard IC pins to control appication. Buttons pull low the IC pins and i can solder a resistor and transistor to mdbt40 module, all while powering everything from onboard cr2320 battery on the remote.

some more resources since new users are restricted to 2 links per post: