I will go ahead and come up with something. It will take a little time, as I'm not the world's best artist lol.
In the meantime, I'm not sure I understood the question in the first post, now that I'm reading it again.
Is your concern that your jacket won't fit over a thick shirt and/or a vest?
If so....
Men's clothing is meant to have more ease than women's. Especially a military uniform that requires strenuous activity without binding or ripping out the seams.
If the difference between fitting and not fitting for your jacket is whether you have a vest on, you have the wrong size for sure.