I have "developed " many ( too many) PIC boards , with various projects in mind, personally i would think BIG and fast (16MIPS) , PIC24 or dsPIC33 with at least 66 pins (53 IO) ,Go for biggest program and data memory (1024 / 32 kb) provide some dedicated peripheral connectors, I2C, Uart, SPI , PWM, ADC, even USB , Most PICs now have PPS to allow fexable external pin connections , include at least one LED to flash at startup, Vdd at 3.3v but some IO are 5v tolerant Power for the Dev board for my projects is best left external .
( Sorry pic a bit fuzzy)