Since I'm worried about the future of AVR, I've been looking into software USB for ARM cortex-M0/M0+ that is similar to V-USB. All I've found is a port of LUFA, which is for MCUs with internal USB hardware.
Now I know there are Cortex-M0/M0+ controllers that do have USB hardware, although I'm looking at using the smallest lowest pin-count I possibly can which usually don't have USB hardware. I know some of these tiny controllers will have USB hardware but they are typically in a WLCSP package which have small spacing between the pads which I cannot work with. This is why I'm looking for a software implementation.
Is there a software only implementation of USB for ARM-M0/M0+?
note: by software, I mean firmware but it seems code-only implementations of hardware peripherals are usually referred to by software.
note 2: Please don't suggest any specific products. The question isn't about an inability to find small controllers with USB, its about the lack of a software implementation of USB for ARM much like V-USB.