To solve problem like you have I would NEVER use any of the flash based parts that do not also have on-board ICIP (In Circuit Initial Programming) as well. Parts without this feature I would recommend you pass over them.

This is one of the reasons I keep recommending the Cygnal parts. Their parts have a JTAG port on each part and if you equip your circuit board with an access connector then you can perform the initial programming with ease. (Note that you can also use this port for reprogramming the whole program in the field without even having to write UART port IAP (In application programming). Plus you get the hardware debugging support functionality of the JTAG port as well.

Michael Karas