DefendX Tactical Smartwatch Hardware Design

Hi,I am building the DefendX Tactical Smartwatch. I need an expert hardware engineer to design the board completely from scratch—starting with component selection and schematics, all the way through 4-layer PCB layout and physical lab testing.

Project Requirements (42×42 mm, 4-Layer Board):
Core: ESP32-S3 (Compact module like the MINI series). Radios: Wi-Fi/BLE, Sub-GHz LoRa (e.g., SX1262), and GPS (e.g., SIM68M). Sensors: Biometrics (HR/SpO2 + Temp) placed wrist-facing on the bottom layer, plus a 9-axis IMU and Compass.
Power & Storage: LiPo battery management (with a central cutout pocket on the PCB for the battery) and SPI NOR Flash.

Your Scope of Work: BOM Selection: Pick reliable components that are actively in stock at JLCPCB/LCSC.

Schematics: Design the circuit from scratch, ensuring proper power domains (3.3V/1.8V) and I2C/SPI bus stability.
PCB Layout: 4-layer routing with strict RF keepouts and impedance matching. Hardware Bring-Up: You MUST be able to order PCBA prototypes to your own lab, power them on, verify voltages, and test basic USB/I2C communication before final delivery.

Design Suggestions & References Welcomed: We strongly welcome any design suggestions, component/architecture improvements, or layout references you have from similar ultra-compact wearable or wireless products you’ve built in the past.

If you are capable of this end-to-end turnkey design, please share your estimated cost and turnaround time. Also, to protect the project budget, if a schematic or layout mistake on your end causes the prototype to fail, do you agree to update the design files free of charge? Looking forward to your proposals and past portfolio references.