Hello @chetferry,
As you mention, the tools in MCUXpresso manage directly the linker script and make it easier to modify it. If you want to shift an application to a determined address, in the properties->C/C++ build->MCU settings modify the range address and the size, this will shift the vector table and all the registers to this new address, this in the application side:

In the bootloader side, in the same tab, limit the region memory so the bootloader doesn't corrupt the application.
Best Regards,
Alexis Andal0on
Best Regards,
Alexis Andalon