Your reasoning is good
I started on insulin almost immediately after diagnosis. It made perfect sense to me and my Doctor. I guess the person you need to convince is your Doctor... having been on insulin for GD should be in your favour.
The big caveat with insulin -- apart from the risks, of which I am sure you are already aware -- is that it gives you the ability to eat as much as you like, cover it with insulin and still have great BG levels... a sure-fire recipe for weight gain
The trick is to manage what you eat so as to minimise your need for insulin.
BTW my son is now 18 but I can think of much more gross things I did than finish off his cereal milk
