I can think of all sorts of modifications people might want to make for their custom-built or remodeled boats. What is the most common modification they ask for? I know I would love to make sure our boat was as family-friendly as possible. We do a lot of boating with the children in our families.
I don't know if there would be one particular modification that people would ask for. It probably depends on whether they are looking to adapt a boat for something in particular, (say for serious fishing), or are more into add ons. My brother is an electronics geek so you can see where his interest would lie.