I've been looking at a PIC16F1455, as a $1 chip capable of USB without a crystal, in a 14-pin package.
But seeing all those interesting STM32F0 chips makes me think whether it's not more productive to change to ARM all together

The PIC32MZ is an interesting.. should be capable of running Linux.
Also, finally, they have got a chip with proper external memory integration. However, with 512kB integrated RAM I don't see when you will need that anytime soon
Not too impressed with PPS on PIC32 though. I tried to design in a PIC32MX470 on a project last month, but it felt more like a clutter than a feature. SPI SCK was not on PPS matrix, not every pin supports SPI SDO/SDI at the same time. Maybe I'm spoiled with the PIC24 PPS where it is like "oh I need timer/UART/SPI, I just throw it on any RPx pin and sort it out when I write firmware"