When companies ask for customization for a SaaS product, it is important to draw the line and not offer one-off customization.
However, if a BigCo is willing to pay a large sum for a standard contract that includes a required feature on your roadmap for the next 12-36 months, it could be beneficial to build it.
This is especially true if there is potential for other big customers to want the feature as well.
Ignoring such requests could result in missed opportunities and potential failure.