I'm not actually looking to move the "logical" address (bank number + 16-bit address) of the functions, but rather I want to modify the hex file so that it places each bank in the specific "physical" address in the Flash or internal OTP ROM (...
Dead easy to edit using CodeWright, I've done it hundereds of times. You may have to sort first.

The microcontroller we are using (Philips SAA5665) has a "linear address" mode available for the address pins in which it expects the banks to be packed into the external code memory (bank0 at 8000H, bank1 at 10000H, bank2 at 18000H).
So does the MX and a couple of others, that I know Keil support. Get away from banking.

I've tried all of the available options for my version of the IAR ... . I'm thinking hard about popping for the price of the upgrade as it supposedly addresses my problem (both situations).
I would consider switching to one of the '51 Specialists (Keil and Raisonance). The Generalists out there such as IAR does not have the same grip on handling the nooks and crannies of an efficient '51 compiler e.g. I have seen '51 compilers that actually placed variables on the stack ARGH.

Erik