The idea is that any new firmware does not include the upper 512bytes of Flash, but as IRQ vectors will change with new firmware but is now part of the firmware-block as compiler Intvec have been moved -512 bytes down. If you put your custom Loader in the upper 512bytes too and as you never erase this block, much less chance of bricking.
I guess opcode for BR could change from msp family? but this does work on a G2553. ?CCS could use pragma location if it can not handle @
Not all vectors are available or used, so you should fill them with random value instead for the BSL password if yo