Any thoughts and concerns would be appreciated. I've played guitar / bass for a number of years now but, something seems to be missing. I'd like my guitar / bass to have custom parts. What's your thoughts?
Please express them in this post.

This is a really broad topic. I don't think their are many guitarists who don't upgrade one piece or another from time to time. After market equipment and parts are a great way to go, it just depends on what particular part you want to change.