For the majority of desktop users (which is where classic snaps are supported) I would assume they would access something like minicom via a USB-Serial converter. These devices should be supported using the existing serial-port plug along with the hotplug feature - see Hotplug support for more details.
Also I think it is a bit of a stretch to say that minicom is a terminal emulator itself, given that you sight the use-cases of serial-based devices and sending serial data etc. Please try using hotplug with serial port as I pointed out above and I think this should be sufficient.