Final answer:
A good way to future-proof and reduce support requests for design changes to themes is by using schema settings to offer merchants control over the changes.
Therefore, the correct answer is: option A). Use schema settings to offer merchants control over the changes.
Step-by-step explanation:
Using schema settings to offer merchants control over the changes allows them to easily make modifications without needing technical assistance. Another approach is to hard code things like color values, but offer settings for element widths, giving merchants some flexibility while still ensuring consistency.
Creating a range of alternative template files with specific style values is also a useful strategy. This allows merchants to choose from different pre-designed options, reducing the need for customizations.
However, hard coding all changes into the theme files with specific style values and grid sizes may make it more difficult for merchants to modify the design in the future, so it is not a recommended approach.