Definitely JLink, love mine.
NXP or STM32. Both are going to have the right sizes and peripherals. Smallest a 2xCAN unit will go down to in either mfg is 64pin. But since you need 4-5x UART you're going to be into the 100pin packages I think. From what I know about STM, the HAL gets no love, but it honestly isn't THAT bad. I don't know what NXP offers for a peripheral library.
Can't say to VisualStudio + VisualGBD. Haven't used it, but seems like a nice inexpensive alternative that isn't Eclipse based.... BUT... Since you are doing ethernet, I'll assume you'll need a driver for that and a TCPIP stack. I'd consider if this is a money making project maybe shell out for Keil "Plus" middleware or Segger makes reportedly good middlewares too.