Mapping stm32f4 pins to motor

I want to use an Omnibus F4 for an octacopter. Normally the board is programmed for max 6 PWM outputs. However this board has some solderpins which are connected directly to pins of the stm32f405. In Betalfight these pins can be remapped to PWM function with the command resouce MOTOR x PAx. I’ve not been able to find how this can be done in Ardupilot. I want to remap PB09->motor7 and (probably) PA10->motor8. Not sure if the latter pin (nr 43 on the chip) can be made available as it seems to be connected to the DSM2.
My question is, can the resources be remapped programmatically. If not, should it be done by changing the firmware?

Hi @mbosschaert

AFAIK the omnibus4pro already has 8 PWM outputs available.

Explained in here.

Indeed the docs indicate that there are two MOTO pads on the PRO version. On the Omnibus F4V3 (actually it seems to be a modified version of eachine :Eachine Wizard X220S FPV Racer RC Drone Customized Omnibus F4 V3-S Betaflight 3. Sale - Banggood USA), the two pins PC8 and PC9 are very hard to access and the two MOTO pads are missing.
Does this mean that I need to recompile new firmware with modified pin-outs or is it possible to remap the PWMs by configuration?