You can accomplish basically the same thing by using very light springs that will allow the mechanical advance to go to full advance at a low rpm. Two light springs should be about right to have the mechanical all in early enough, but still have enough spring tension to return the mechanical advance to rest w/the engine off. This negates the need for a starter switch, while still giving all the available advance at low rpm.
A page w/some more info: Limiting/locking mechanical advance
If you remove the weights and springs and use tie wraps, etc. to lock the liming, DO NOT
remove the cam of the mechanical advance mechanism. It holds the advance plate to the center shaft.