Bootloader for Arduino OTA DFU

Description

Hi,I am looking to implement secure Over-the-Air Device Firmware Updates (OTA DFU) capabilities for an Arduino-based Bluetooth Low Energy project utilizing a nRF52840 microcontroller. The current firmware is written for the Adafruit Bluefruit Feather Express board using Arduino and Adafruit libraries. However, the existing OTA DFU approach only supports legacy unsecured connections.
I need assistance developing a simple proof-of-concept demonstrating secure OTA DFU via Bluetooth Low Energy between the Feather Express and either the nRF Connect or Adafruit Bluefruit mobile apps. The solution must be compatible with the Arduino IDE to maintain compatibility with our existing codebase. Modifications to the Adafruit library are acceptable as needed to enable this functionality. Solutions relying solely on the Nordic SDK will not meet our needs unless the code can be ported back to an Arduino-compatible format.
The deliverable would be a working example Arduino sketch (blinky) demonstrating OTA DFU via secure BLE to validate the approach before integrating it into our application and product firmware (not part of this gig). Please provide your rate for developing this prototype BLE OTA DFU solution within the Arduino/BLE ecosystem to meet these requirements. I look forward to reviewing any bids for this project.