Well, if your ok with the non-realtime characteristics of the RPi's GPIO via linux userspace, one might as well just buy one of the dozens+ of USB->GPIO adapters all over ebay/amazon/aliexpress/etc with windows/linux/etc drivers.
Or if you need something more advanced than basic LED blinking/etc, just pick up a wemos D1, or any of the dozens of other similar microcontrollers that can be had for a dollar or two that have GPIO and a USB serial interface and do your bitbanging on the ESP8266/etc in an environment that isn't susceptible to a heavyweight OS failing to schedule your task for long periods of time. One can hang that device off a PC and talk to it with simple serial programming/commands or just plug it into the target device as a wifi adapter and do all the control over Wifi+JSON/etc. Which it turns out are basically what most of the USB->GPIO adapters are anyway.
So, in the end, using a RPi for this is really sub optimal on every front, cost, performance/accuracy, complexity, power utilization, etc.
There are many cheap system-on-a-chip microcontrollers that have enough computing power for many basic uses for which RPi is overkill, and some GPIO and built in wifi and/or bluetooth wireless, and they support dev frameworks like arduino or micropython.
Or if you need something more advanced than basic LED blinking/etc, just pick up a wemos D1, or any of the dozens of other similar microcontrollers that can be had for a dollar or two that have GPIO and a USB serial interface and do your bitbanging on the ESP8266/etc in an environment that isn't susceptible to a heavyweight OS failing to schedule your task for long periods of time. One can hang that device off a PC and talk to it with simple serial programming/commands or just plug it into the target device as a wifi adapter and do all the control over Wifi+JSON/etc. Which it turns out are basically what most of the USB->GPIO adapters are anyway.
So, in the end, using a RPi for this is really sub optimal on every front, cost, performance/accuracy, complexity, power utilization, etc.