Does anybody know if it is likely to be possible to program options not available through the interface?

there is an option to turn off filtering and pre/de-emphasis. Set register 58 to 023B

My current option for doing this is to physically hack into the serial bus, insert a switching chip and use a raspberry pi to switch control away from the radio's onboard microcontroller chip to the raspberry pi serial GPIOs, program this option into the RDA1846 and then switch back control to the radio. Pretty heavy work for something that might be possible in software by programming the onboard controller (using CHIRP).

Any guidance very much appreciated.
Julian M1CWA