A Sustaining Engineer usually inherits all of the constraints of a previous design with none of the freedom! Except for reducing BOM costs, there may be no allowance or budget for any change whatsoever.
But when an ESD problem arises, the Sustaining Engineer may have a limited subset of options for recovery as compared to Production Problems.
But for BOM cost reductions, the risk to compliance must be considered.
If Susceptibility Scanning shows no quantifiable reduction in robustness or increase in susceptibility by removing a TVS device, then the confidence factor in the cost reduction goes up and can be justified earlier in the product cycle.