Custom Thin Touchscreen MP3 Players

I need guidance and hands-on help to create two bespoke touchscreen MP3 players that are slightly smaller than an iPhone, noticeably thin, lightweight and visually striking. My goal is to tailor both the hardware and the software, not just re-skin an off-the-shelf model.

On the hardware side I want full freedom over shape and overall form, precise button layout, exact size, colour accents and even the material choice so the devices feel premium yet stay light in the hand. Internally, I expect recommendations on components that will keep the profile slim while still delivering solid battery life and audio quality.

For software, I want a clean custom user interface, expanded playback options and the ability to add or edit features later—apps, controls, connectivity upgrades and anything else that future-proofs the player. Bluetooth and Wi-Fi should be treated as core functions, not optional extras.

Please walk me through the entire process from design concepts and 3-D modelling through prototyping and firmware build, outlining what you can personally deliver or manage and what would need outside suppliers. My immediate milestone is to understand practical constraints (cost, tooling, minimum runs) and receive an actionable plan that leads to two functioning prototypes ready for real-world testing.