Can the bootloader on the ADuC702x chips be overwritten accidentally?
No, this is not possible.The bootloader is together with calibration and chip identification information ina factory programmed area on the chip and is protected against accidental erasure.
Note that all ADuCxxxx parts contain firmware called a kernel which contains the bootloader, callibration code etc. This kernel runs after any reset before entering user code. This kernel can not bee viewed, executed or accessed in any way by the user.