The main issue is mission assurance. Using the stack or the heap means your variables aren't always at the same memory address. This can be bad if a particular memory cell has failed. If every variable has a fixed address, and one of those addresses goes bad, a patch can be loaded to move that address and the mission can continue.
This seems like a rather manual way to go about things for which an automated solution can be devised. Such as create special ECC memory where you also account for entire cell failure with Reed-Solomon coding or some boot process which blacklists bad cells etc.
This is what make remote debugging possible. It is impossible to do interactive remote debugging over a ultra low bandwidth link. If everything have static address and deterministic static, you can have a exact copy on ground and debug there.
A local exact replica with deterministic state save lots of time.