The Product is Finished, so Let us Make it Safe!
A similar situation occurs when the requirement for functional safety only arises after the product has already been fully developed. Or an existing product should now be sold with a SIL, a PL.
In almost all cases such a situation means to develop the product completely new, because many aspects of functional safety affect the hardware and software architecture, e.g. isolation of channels from each other, software architectures without "hidden data flow", even the choice of programming language and components (unfortunately nothing works without the manufacturer's safety manual, so you can only use a limited selection). Therefore it makes more sense to include functional safety in the project from the beginning, so there are no massive corrections at the end.
What can be worthwhile on the other hand are rapid prototypes or functional samples to minimize risks. These also allow safety aspects (e.g.: is the computing power sufficient for the safety mechanisms?) to be clarified in advance.