Volley. You might not have the reactions and quick feet of a pro - which is what makes their volleys better then amateurs. But you can hit a competent volley. It's not a complicated shot.
If you realistically have 40 hours a week and money to spend on serve practice/physical training - you could develop a pro like serve (at least a female pros) in a few years as well. But of course I haven't tested this theory.. Who has 40 hours a week to spend on serving - stretching - exercises for throwing and lessons.. The only thing that helps this shot is that is something you can practice by yourself effectively. Volley with a ball machine is pretty close of course. The simplicity of volley makes it the top choice. Especially if the pro is Roddick.. I kid..