I see his point but only you can best say how well the "action plan" would be received. You know your wife and if you think it would start WW3 and produce nothing positive then make a call based on your own experience with your wife. Here's where you have to manage your Lawyer to what you know what works and doesn't work with your specific situation, (as if you didn't already have enough on your plate).
If you decide to do the letter use email it so you have date/time stamps and any record of her response. You don't have to start with.. upon advice from counsel.. yada yada. You could always say putting it in writing let you compose your thoughts in a concerned and loving way.
Or you might just pull the trigger on filing an haveing her served like I did. But in my case she was expecting to be served at that point so it didn't just fall out of the sky.