Although after some time, I would also vote for having ability to set user baudrate. Just let the combobox be also editable and when user enters "non-standard" baudrate (which means baudrate you don't know) just issue a warning but do not disallow it, just pass to the com init structure. This would be helpful for us too. We had to implement own flash tool supporting 125000/250000 baudrates (suprisingly working 
).
).