Asterisk GSM channel driver?

Hi, I have seen, that there are channel driver for the DECT project, where you can connect your DECT handset to the Asterisk PBX. There is also somehow a possibility to connect a mobile GSM phone via openBSC and asterisk. But has somebody thought about just connecting the osmocombb mobile phone (which is connected to a public mobile network [or openBSC]) to asterisk? I would think of making a call through a channel driver, osmocombb is doing a call like "call ms number", but instead of using mike and speaker asterisk would send the already in GSM-codec modulated voice data through the serial port (maybe it would needed to use the non-standard USB-TTL version to handle full duplex GSM speech). And layer1 of osmocombb could send that nearly untouched on the air. For incoming calls this could be similar + signalling the call through the channel driver. Has somebody already thought of that? Would that be a achieveable task or is it technically impossible? Thanks Tim