A few things
1. I agree that a developer's time is limited and the cost/benefit ratio must be considered. However, in the case of merging and the work required, it seems that there are some people that would happily do the work of properly merging the BUG mod and supporting it if you asked.
2. Performance and speed is of course a valid concern. My guess is that the BUG mod would not significantly affect the base game speed. One never truly knows until one tests of course, and a test would be relatively simple to do.
3. Regarding complexity, option inflation, etc. The BUG mod doesn't actually change the game it just compiles and presents information for the benefit of the player. The BUG mod options are by themselves accessible only by a Keystroke and are not cluttered with the already existing game options.
4. Regarding Value of the Options themselves. If points 1-3 are correct, then adding the BUG mod requires little to no effort on your part, and is of value to those who use it even if it's not much value to you.