Re: USB servo via trinket
keep in mind that USB fake serial is designed for people who do not want to learn how to use USB properly
the majority of the setup process for the fake serial port involves... well... some hacked up solution that makes a fake serial port, this complexity in the installation is the trade off for simplicity in the usage.
you sound like the kind of guy who might benefit from using true USB protocols. a servo controller sounds like the kind of application that might benefit from using simple control request messages. You'll end up with better responsiveness, it will be less error prone, and it will take up less code space. This is because control requests have a defined structure. Remember, "serial" is not inherently packetized, while control requests are. A servo controller is definitely something that benefits from something packetized.
If you use "serial" instead, then you'd have to define another custom protocol layer and thus write a parser for that layer, which is always a pain in the ass. Also my fake serial protocol is not designed to be fast.