That’s nice - the STM could do the CTCSS generation and detection.
But the connection to the host computer would be by USB - no? That is where the problems are right now. So you would still have those problems.
Of course, I suppose it could use a different format where perhaps larger chunks of data are transferred at one time. Or the connection could be by SPI? That might make it RPI-specific though.
Food for thought.
Ken