Hi,
re-programming should definitely work, it's a main feature. If initial hook won't occur once there's some code already in the MCU, it may be caused by RS232 level shifters not properly working fast enough after power-on. Then PC won't see initial ACK from the micro.
To confirm this, try to use RESET pin of QB8 (if enabled) or power RS232 shifters from separate supply (dirty way is to short-connect MCU Vdd for a short while).
For 8-pin QG8, porting code to IIC would be a huge effort instead of adding software SCI functionality (that was me promissing doing it in May ; ). Similar way like on QT/QY family. Once this alpha software is available, I'll let the forum know.
Regards,
Pavel, ok2ucx
Freescale Roznov, AN2295 author