I think it's a great idea. It's your gun. I wouldn't engrave it into an original, but this is not the case. Besides, call Jum and but another side plate and you could always change it for what ever reason?
I inlet a small oval of Lagan's Elm into my Kibler on the bottom between the trigger gd and a toe plate I added. It is distinctive. Soon as I learn to engrave well enough or carve, I am going to add Logan's Elm to it.
Aren't they great guns?
Mine just drives tacks all day, same hole after same hole.