Arduino board modification

PCB design. Modify the Arduino DUE dev board with minimum requirements, such as adding an Ethernet port, stripping down to essentials, "Ruggedizing", adding isolated contact output relays. In other words, I'm want a rugged I/O device. As for the software, I only want C++11 code to test that all the I/O's, LED's, comm ports are working as expected. Furthermore, since this is a final design, your advice, consulting, changes and suggestions are very welcome and encouraged. ------------------------ Main board 1. 512kb EEPROM (possibly connected through I2C?). Is SD card slot a better idea?? 2. 1 Ethernet port 3. 1 Serial port RS-232 4. 1 Serial port RS-485 5. 1 USB - for loading firmware (micro A/B) – no USB power needed 6. 1 Temperature sensor (does this require calibration? Is it possible to have one where calibration is not required?). 7. Proper electrical shielding. Device will be installed in a harsh environment 8. High/low temperature withstands -20 to 60 degree Celsius. Device will be installed outdoors in another waterproof enclosure. 9. Replace components for harsh environments (for example better capacitors) 10. Low power consumption since battery backup may be used. 11. Try to limit the number of PCB layers as much as possible. 12. Strip down any other extra components and circuits not need to reduce production costs. For example, power plug, reset button etc… 13. Remove ability for powering up using the Native port USB 14. Move the programming USB port and instead add pin headers so it’s only accessible from inside enclosure. I/O Board (pluggable terminal blocks all Optocoupled) 1. Digital output - rated to ~10A @ 250VAC, 10A @ 30VDC (via form C relay contacts) 2. Digital Inputs 3. Analog inputs 4. Analog outputs Power Supply 1. 12-24VDC input. Regulated, fused power supply. Isolated supply to relays if possible. 2. Fuse with fuse holder. Accessible from outside of enclosure. 3. Screw hole on PCB for connecting chassis ground. Enclosure 1. Need to fit the board in an enclosure very similar to this... Example enclosure  Link Deliverables: 1. Schematic diagram (i.e Gerber files etc..) 2. Bill of Materials 3. Board dimensions 4. Test C++11 source code to test all I/O functionality (including LEDs, USB, Serial) 5. Produce and deliver 3 working PCB units for software testing.