It's not a bad idea, Crimson. It really isn't. Not sure if it's a good idea, either... and that's the crux. How each of our sitches is unique in the choices and actions of no less than two individuals.
On your second post, it is interesting how you indicate you do not want your W to know that you are happier without her. Do you notice how that is very similar to the roller coaster of the WAS or MLCer, dragging the LBS back onto the roller coaster?
Do you want to drag your W back onto your roller coaster, or be dragged back onto hers?
Really, there is one thing and one thing only, here:
Do... or don't do... neither one right nor wrong... Regardless of what you choose, know that there will be both benefit and harmful consequences.
Every moment that you do not send the letter is another moment... hour... day... that you are CHOOSING an action. Because you are afraid.
If you are afraid of sending a letter that is not going to be effective and not have some expected results, then what are you brooding over it for?
And if you are NOT afraid of sending a letter, regardless of how it may be interpreted, then what are you waiting for?
No one is a pro at DB in the same way that no one is a pro at R or in child rearing or at life.
Do or don't do and accept your choice and move forward. As harsh as this may sound, it really is that simple.