New arduino mega - PCB Design

Hello! I need to make changes to the Arduino Mega so that it can be used for my specific applications.

I need to use the electronic diagram of the Arduino Mega PCB board and implement the following changes:

- Touch screen display interface;
- change the connectcores;
- add the RS485 communication/conversion module;

This is all on the same PCB.

In the end, I intend to have:

- Electronic PCB design in DesignSpark file or compatible format;
- GERBER files ready for production
- BOM file filled out with manufacturer and seller data
- XY files
- Stencil files
- PDF including schematic and board layers
- Pictures of the possible design (software generated)
- 3D model * (step file)
- Source files of the project

Attached, example of the final result, after production