PCB design for Bluetooth Microphone

Hello, we are developing a Bluetooth Stethoscope to improve listening to internal body sounds. Below are some of the design ideas & constraints for our device. Design ideas and constraints PCB: Dimension would be max 20mm x 80mm. Microphone on one end of the PCB and the Mini USB on the other end. On/Off Button roughly centered. Device will be connected to a stethoscope on one end, same as mic side. PCB should have 4 small screw holes for assembly to housing, holes may be used for pin holes. Bluetooth: Bluetooth classic may be one of the only options for this device because Bluetooth LE is not yet capable of streaming high quality sound. This is not a heartrate monitor device, but rather a higher quality sound streaming device for internal body sounds. Bluetooth LE will be a future project for this device when the tech catches up to high quality sound. Sound quality will be a high priority with this device. Ideally the device would use a Bluetooth SoC chip but we are open to other solutions if there are better and cheaper alternatives. We’d like to keep the programming language for the chip as simple as possible and use the chip’s SDK for most of the code with only small changes. We like Nordic chips but I am not sure if Nordic has the right chip for this application and the chip would have to be in inventory of the PCB manufacturer. If possible use a Bluetooth chip with built in antenna with FCC compliant certification. Microphone: The device being developed is for listening to internal body sounds like a heartbeat and using Bluetooth to listen to those sounds and record them with a smartphone. The microphone on the device will most likely need amplification. I have an amplifier circuit diagram that I know works and will post that also, but the circuit we have uses analog microphones that would need to be converted to digital to be transmitted with Bluetooth. I would consider MEMS microphones if we can still get adequate amplification. MEMS mics might be a better solution due to lower noise with MEMS microphones attached to PCB. The simpler the design the better but it has to work and amplify faint sounds with minimum noise. Power: Powered with Lithium Battery. PCB will have connection for battery to plug directly into PCB. No soldering of wires for battery connection. Manufacturing: My plan is to have the PCB built and assembled in china probably by JLCPCB or other similar company with SMD/SMT components. The Bluetooth chip would have to be an item in inventory with JLCPCB or whatever manufacturer we go with. Final assembly would be done in the US and would include plugging in the battery and assembling the cover to the PCB. We are trying to keep assembly simple in the US due to high cost of labor so no soldering in the US, just simple assembly. Buttons: One button should be enough for this device. The button would turn the device off and on. Sound level of device would be controlled with an app on a smartphone. LED: LED would indicate device is on or what mode the device is in, such as pairing or advertising or connected. LED would be near On/Off switch and bright enough to easily see. Looking forward to working with you and getting this project going. Thanks for your consideration.