AVR UC3 chips

What I am trying to do is have a package that has 4 channel 12bit ADC, at least 4 UART, one USB for programming, and be compatible with Arduino IDE. I'm looking at staying close to the cost that a Uno is as I have to add a RS485 to the 4 UART, and integrate ethernet OR wifi. By using an external ADC, this adds cost and complexity.