So my ever so lovely suede coat gave me a bit of grief last year because the armholes are a titch too snug for my liking. I know there isn't any spare fabric hiding in the seams, so I was going to aim to rip it open along the bottom of the armpit on one of the seams, and then add an extra panel of fancy thick weight matching fabric. Do you think it can be done? I'm having trouble finding any instructions for it, and I'm not the finest at BSing this kind of thing. I don't want to have to pull the whole arms off (if possible), or potentially ruin the coat. Can anyone give some advice on where I should go with this? I'm even open to adding a panel along the top of the arm sleeve if that is a simpler thing to do.
For those that don't know, my coat looks like this:

And here is a not so clear pic of what the seams look like on the underside of the arm hole:

