Are you having issues with it not starting due to the immobiliser or just locking/unlocking? If it's immobiliser problems then the spider could be a suspect but if it's locking issues then it's unlikely to be an issue with the spider unit either the fob or the alarm ECU is more likely to be suspect.
You could go the down the road of an aftermarket alarm with central locking interface - the alarm ECU stays in-situ but basically does not get activated.